I think the main reason for pianists like Buniatishvili and Wang gets criticized is for the way they dress in concerts, which I suppose you could say are a bit more on the revealing side at times. Some listeners might think they use this as a way to gain attention or to show off, though this really doesn't mean much and it might simply be the style that these performers wish to present themselves in.
Now for the playing, I don't always agree with Khatia's playing but in no way is she a "bad" pianist (Given she's probably better than everyone on this site )
People who do that are just projecting a lot of whatever sh*t is going on with them IMO. Probably repressed jealousy of what they believe is the other person's good looks or liberated sexual self-expression. Like if you are happy in your own life and skin, how somebody else chooses to present themselves 50 meters away on a stage simply won't bother you. Or if it does, you'll choose to not attend the concert, not shout about it on online forums.She is a very skilled pianist and I think she can be very lyrical and sensitive in some slower pieces, such as in these recordings: What I don't like about her playing is that she sometimes takes either a very fast tempo so that she makes a lot of mistakes, or she is just a bit sloppy. Now, I have no problem with wrong notes, but there is just something about how she does it that comes across as intentionally careless or that she is not doing what she is doing to serve the music. It feels sort of arrogant or... something, I can't quite put my finger on it. I don't know what's going on but it makes me feel like she has the potential to be a pianist I'd truly enjoy a ton if she just stopped doing... whatever it is she is doing when she takes these really fast tempos and/or plays a ton of wrong notes while sounding kinda like she doesn't care. I have a feeling this is what bothers some other people too.