There's several issues here:
1. Using cameras to evaluate skating isn't the same as for a tennis ball or even a baseball strike zone. For whether a tennis ball was in or out, it's easy; the software just needs to figure out when the ball hit the ground and align it with the line marking the edge of the court as a reference. For a strike zone, it's a bit more difficult because there's no direct reference point (i.e. the ball is in midair rather than touching the ground), but it's fairly straightforward to interpolate between the pitcher's and catcher's positions. For skating, the challenge is much more difficult. Under-rotations are based on the skater's path of travel over the ice, so it's not just a single measurement. Instead, you'd have to figure out the path of the skater, and then use that as a reference for the skater's landing. You'd also have to figure out not just the position of the skater's skate, but also its orientation. Edge calls also depend on determining the skate's orientation. So it's not just a single frame that you can show the viewer, the way it is for seeing if a tennis ball was in or out.
2. Furthermore, a lot of the rules are not as specific as you'd expect. For example, how do you define a skater's path of travel in the air during a jump? Ideally we may want something like the path of the skater's center of mass, but good luck figuring that out when the skater not only has an irregular shape (i.e. not a ball, cube, etc.) but also an irregular mass distribution, plus clothing on top of that. So instead, you may use something like the tracing on the ice. But what is the line of motion that you would use? Taking the (counter-clockwise) flip as an example, it's pretty clear that the landing spot would be one point of the line of travel. But do you count the starting point as the right toe-pick point? The end of the left foot glide? Maybe an average of the two? It's actually not so clear. Additionally, when measuring the orientation of the skate on landing, at what point do you make the measurement? Is it right when the toe-pick touches the ice? Is it when the (non-toe-pick) blade first touches the ice? If you say toe-pick, then it encourages skaters to land more flat-footed to avoid under-rotation calls (since there's some rotation between when the toe-pick touches and when the blade touches), which would lead to more wear-and-tear on the body and less control coming out of the landing; as already mentioned, it would disfavor some skaters like Mirai who tends to point their toes a lot on landing.
3. A corollary to this is, what defines a good jump? For example, I'm guessing that what a judge looks at to determine under-rotation is not actually the skate's orientation at the moment of landing (which is the basis for its definition), but at how that landing affects the skater's body, in terms of speed going out of the jump, if the free leg swings wildly, the path of the landing leg on the ice, etc. Focus on these more technical aspects (i.e. under-rotation) may lead to less emphasis on other aspects of a jump that makes the sport aesthetically attractive (such as carriage, flow, etc.).
4. How much would the system be adopted? I'm not talking about whether or not the ISU would use this kind of thing to replace judges at the Olympics. I'm talking more about at what level of competition would people be expected to use this type of system. Do you use it on basic skills tests? Juvenile competitions? Etc. Although I know both IJS and 6.0 are still used, it's a bit of a bureaucratic mess to manage different scoring systems -- one that's done via software, and one that's done via the human eyeball.
Having said that, my thoughts are (these are similar to a similar thread from just after the 2014 Olympics):
There's a lot of data in videos. The problem is generally not whether or not there's enough data, but whether or not we can generate good enough algorithms to process that data and extract the information that we want. Conceptually, however, it's not that difficult to do. For example, the path that each skater took in their Olympic programs is already worked out; I remember seeing Youtube videos at the time, so either those guys used an algorithm or they drew it by hand (I don't know which). Even if they drew it by hand, if you have a video that captures the entire rink, it's actually not that difficult to calculate the skater's position in any video frame relatively accurately (i.e. to say within 10-20 cm). I demonstrated how this could be done in an earlier thread; I would guess the Veriskate guys basically do the same thing. After calculating the skater's position for multiple video frames, it's fairly straightforward to work out the skater's velocity. For a jump, it's just a matter of taking the skater's position at the beginning and at the end of the jump, and dividing the difference between them with the time elapsed (calculated via number of video frames elapsed) to figure out the (horizontal) velocity, air time (and thus jump height), etc.
Next, figuring out under-rotations. Regardless of whatever rule you adopt, you need to have a way to accurately measure the skate's position on landing. This can be done via slow-motion video of the landing skate. However, we have to be cognizant of visual distortions (basically, it's zoomed in from far away), and the human eyeball is pretty bad at accounting for this, but algorithms can compensate for it. Basically you just need to determine the skate's orientation with respect to the camera, and if the slow-motion video is clear enough (i.e. not blurry), this should be doable. You can also check for correct edges in this way.
In short, I don't think it's all that difficult to actually measure, relatively accurately, various parameters of interest of a skater's jump such as the height (calculated from air time), distance traveled, landing rotation (i.e. amount of under-rotation), and take-off edge, from video. In fact, I think the only videos that you really need are:
1. A "wide" view of the entire rink while the skater is skating. This will give the skater's position in the rink at all times. If the video has good enough resolution, it can also be used to determine the position of each skate (for things like jump take-off and landing locations of each skate).
2. A "close-up" slow-motion view of the skater's skates at the times of interest, i.e. take-off and landing of a jump. This will give the 3-D orientation of the skate relative to the camera. If the camera's position within the rink is known (such as if it's within view of the wide-view camera), then the orientation of the skate relative to the rink, and hence of the jump's path of travel, can be calculated. From this, how much under-rotation occurred on landing can be calculated, as well as the take-off edge.
That's it. The rest is just developing the algorithms to make this work. The question then is what incentive is there for the ISU to bother adopting this type of stuff.
In fact, my claim is that this can be done largely from the videos that are already out there, and so it's possible to give a good analysis just from available Youtube videos and such. My evidence is to actually do it from past videos, specifically, videos from the Olympics, mostly because they're relatively plentiful (it's hard to find fancam videos of joe schmo competitions, and even of many of the Olympic performances). A rundown of the process is:
1. The entire rink is visible in the "wide" camera. The rink's dimensions are known (at least, I hope it is, I assume the Olympic rink was an "Olympic-sized" 60 m X 30 m). From perspective geometry, it's possible to calculate the X-Y position of the skater's skates relative to the rink to within the pixel size of the video. From the Olympic fancams I found on Youtube, this error was generally around 20 cm or so I think. (Don't have the spreadsheet in front of me right now, might be fuzzy on some of the details.) This is just from ordinary handheld cameras, a more specialized camera would give better precision. From this, the skater's X-Y coordinates at jump take-off and landing can be calculated. I posted a demonstration of this a while back, even giving a grid of points across the rink calculated from the measurements.
2. Figure out the position of the "close-up" camera. It turns out that the camera used for the network close-ups was in some of the fancam videos that I found. Therefore, I can determine its location relative to the rink pretty accurately (again, within 20 cm or so).
3. Figure out the orientation of the skate relative to the "close-up" camera on landing a jump. This is probably the most difficult part. However, I can get a good approximation of this by comparing images of the skate as it's in the air prior to landing (as it's rotating). From the orientation of the skate relative to the "close-up" camera, combined with the skater's X-Y position at the beginning and the end of a jump, how much under-rotation occurred can be calculated. It's more difficult to determine the inside/outside edge on take-off but that can be done as well once the orientation is determined.
During the post-Olympic discussion I did this manually for some of the most-discussed (i.e. controversial) jumps, but never got around to doing it for all of them nor writing up the procedure so it never got posted (yet). IIRC (spoiler alert), though I don't have the spreadsheet in front of me so it's just from memory right now, the punchline was that Yuna's LP second 3Lz was around 120 degrees under-rotated, Mao's LP 3A was over 135 degrees under-rotated, and Adelina's LP 3T was around 160 degrees under-rotated. None of those were marked with a UR call.
Of course, officially, anything over 90 degrees is supposed to be marked with a UR "<", but this hints at an even deeper rule that was often-ignored in the judge debates: The rules say something like if it's questionable, it should be resolved in favor of the skater, and the judges (IIRC) are evaluating the jumps in real-time so they're not using slow-mo frame-by-frame video for UR calls the way the Internet does. For example, if the skate was 100 degrees under-rotated, unless the judge can differentiate between this and 90 degrees under-rotated, it wouldn't get called. (Keep in mind that if a skater is rotating 5 times per second in the air, he rotates 10 degrees every 5.56 ms.) This makes all the Internet caterwauling about why some jumps weren't called UR kind of pointless if they were relying on super-slow-mo and hand-drawn angles (remember, the human eyeball is very bad at estimating angles from an image when it's been distorted due to zoom). The question then is *how* much leeway beyond 90 degrees the judges give in practice, and whether or not this leeway tends to be lower for some skaters and higher for others. My original plan then was to calculate the amount of under-rotation for the jumps that *were* called UR and compare those to ones that weren't, to figure out this leeway (noting that it may vary by jump), but it was very time-consuming and eventually the threads were archived anyway.
But TL;DR -- it's doable, and the question is really whether or not the ISU would be interested in investing in this kind of thing.