It makes me sad too; everyone I know who's seen says it's a great movie, and everything I've osmosed of it from the fandom makes it sound like a lot of fun. I still think the character designs are awful and there are some fans who didn't like it, but Meghan McCarthy seems to have done the impossible and turned a really horrible idea into a really good movie that was liked/loved by almost everyone who saw it. I was mostly convinced before its release that it was going to be nonstop suck because the human designs look so ugly to me that I was sure it had been farmed out to some hack animation outfit that had no connection to MLP at all, but it was all the same DHX production crew, and was essentially just a three part episode of the show. It's a good movie.
I still won't be watching it, and that honestly does make me sad; but it's full of humans, and humans ruin everything. I really appreciate that McCarthy set it up in such a way that the magic mirror automatically converts anyone passing through it into the correct file format for the destination universe's operating system; that means no humans in Equestria... but only as long as she's the one calling the shots writing-wise. If I had thought of it, I would have put "HOERS NOT MUNKY" on one of the signs, because that's what my personal take on the whole thing boils down to. As long as Friendship Is Magic was its own universe, separate and apart and completely human-free, the Ponies were free to be real characters in their own right; Lauren Herself specifically wanted to limit the amount of humanlike behavior to emphasize that they weren't pony-shaped humans, they were ponies, and they acted like pony people would act. Once you introduce humans into that world, the whole thing is ruined, because forever after the Ponies won't be people any more, they'll just be cartoon animals, nothing more than pets and "animal companions" for the human characters, and I say NO. No Megans. No stupid ape creatures ruining a beautiful fantasy world where the little horse folks are people all by themselves without having to be strained through the filter of a primate's interest in them. It cheapens and demeans the entire fascinating world that they've spent the last three seasons building, and it turns everypony in Equestria into some dumb ape's sidekick.
I was completely wrong about it being terrible; what I've heard of it makes it sound like a movie I could really get into and be a huge fan of if it was about a generic cartoon animal princess from a cartoon animal world getting stuck in a real world (or at least more realistic) human high school and having to adapt. But it's not. It's a FIM movie with humans in it, and I just could not enjoy it on its own merits because of that; I would be miserable and angry the entire time. HOERS NOT MUNKY.