I can only answer for myself, but I fell in love with their skating during their 2009 Junior Worlds FD. They had a real softness, beautiful edgework, classic beautiful look, an organic way of dancing rather than a theatrical one, and a real authenticity and innate but reserved musicality with depth that I found similar to Michelle Kwan and still find rare in ice dance where so much of it is putting on the usual ice dance style of expression I've seen from when I fell in love with ice dance thanks to Anissina/Peizerat. I also found their precise, clean style a real breath of fresh air when so many didn't have that quality.
To me, their beautiful posture, line, deep knees, a Yuka Sato type of edge work that was developed when they started out skating as kids under the tutelage of Janet Lynn's coach, Slavka Kohout (Kurt Browning said he loves that they have the rise and fall on their edges that reminds him of Shae-Lynn Bourne and Scott Hamilton), and their really restrained and thoughtful way of expressing music which I still find to be DIFFERENT and DISTINCTIVE in ice dance. The last part is probably what turns some off of their style as they give off the impression that they are limited as dancers (Maia a bit more than Alex). Marina turning Maia into a gorgeous dancer with beautiful posture and line can prevent her from really being free with the upper body. I do think they've really worked hard at it, but they will never turn into the sort of ice dancer many are used to seeing, but instead they are becoming much better versions of themselves.
I also think they do lack the power of say Weaver/Poje (love their power!) and Hubbell/Donohue, so it gives people the impression that their skating skills aren't on par, but there's a lot more to skating skills than just looking at raw speed (as was explained to me by a much more knowledgeable poster) and there's a reason why the Shibs receive some of the highest SS skills scores in the world. I also love their unison and how well matched and partnered they are. They don't have romantic chemistry, but they have the most natural chemistry between one another because they're siblings and grew up with one another for almost all of Alex's life and all of Maia's life. That bond is apparent for all to see. IMO, they are the best team when it comes to that.
I also love their intelligence and personality that I get from their off-ice personas. They put so much thoughtfulness into their skating and I love what they've been giving us since they've taken much more control over their creative direction rather than going along with what Marina wants them to do. So really, it's a huge slew of factors. Either you appreciate them or you don't. No need to force it.