Back when they did the Eleanor Rigby FD, Dick Button said Meryl and Charlie had a sexual connection in the dance. And there indeed was a different energy in that performance than we've seen since, IMO. I think Charlie's loyalty to Tanith might limit him somewhat.
Okay, I'm going to get long-winded and possibly weird and suggest that maybe going up against a team who were marketed as sweethearts and known for their romantic chemistry might have influenced Meryl and Charlie to perhaps look at Tessa and Scott and think, okay, that's their thing, not ours. Marina said in an interview that they didn't have the connection Tessa and Scott do so they had to find another way to win. So maybe their chemistry suffered in 2010-2012 because they neglected to prioritize it in the process of looking for those other ways to win? On Tessa and Scott's reality show, we saw them practicing their chemistry. People mocked it or said it was staged (which it was, to some extent) and we also saw Marina constantly telling them stuff like FEEL THE LOVE!!! during their practices, to just go out there and show their love. And I thought it was interesting to see how much Maks prioritized their chemistry in his rehearsal packages with Meryl, like when he was telling her they could just stand and stare at each other and it would be more powerful than anything else they did. And we saw them rehearsing and discussing the embrace in their rumba and the near kiss in their salsa and stuff. I think a lot of people think that's showmancing and just for titillation, but I think there is this idea that chemistry is something that just happens (as if it's either there or it's not) when in actuality chemistry is something that performers can create together. It's not like Maks and Meryl immediately had amazing chemistry. He barely looked at her in their first performance despite her looking at him constantly. Their first two performances really catered to Meryl's Disney/ice princessy appeal, with references to her figure skating and Mickey/Minnie Mouse. They didn't move past that until their foxtrot the third week.
Anyway, I'm just saying that my guess about their MIA chemistry in 2010-2012 would be that they just neglected working on it as much as they should have been -- I don't think it was about Tanith or anything else. I assume they did some soul searching after their losses in 2012 about how to beat Virtue/Moir, and that's around the time they said they were working on their on ice connection. And I do think it's gotten a lot better since then. They seem more connected in general and they have choreographed lots of moments into their routines where they look at each other and connect.
And yeah, Charlie and Meryl definitely have a more Disneyfied, sweet chemistry, but I think that's fine. Charlie and Maks could not be more different. Meryl carries the shade and darkness in most of her programs with Charlie. My favorite quote about them this whole season was a Russian journalist telling Marina that they are like (loosely quoted by memory) something out of a fairy tale and you don't know if Meryl will remain beautiful at the end or transform and bite the prince's throat. With Maks it's totally different, she has this completely opposite role where she is bringing the lightness to their chemistry and he is the more fiery presence. So it's not this simple thing to me, where you can just be like oh she has much better chemistry with Maks and Charlie was holding her back all these years! They're different men and different performers, and it's a different connection that she has with each of them. I appreciate both!
And like her mom mentioned, Meryl herself made the connection between her increased artisticness on the floor and the decreased technical requirements, which totally makes sense. Especially considering that Meryl and Charlie skated against an incredibly talented team like Virtue and Moir and needed every COP point they could milk out of their programs.