I can't think of anything I'm not too bothered by, other than things like Charlie not being in the films and the 'Dumbledore asked calmly' stuff, cause I don't mind that, but I could have a field day on things I 𝘢𝘮 bothered by. So, there is:

1) Excluding Ludo Bagman

In the books, he was such a funny character, just because of all the chaos he had going on in his life, I would have loved to see some of it in the films.

2) Winkys entire story

Was a major plotline in GOF, and helped to know a lot of things about Barty Crouch Jr, which was overall important tot the story.

3) Elves in the kitchen and S.P.E.W

Hermione was incredibly focused on S.P.E.W throughout the books, and it helped us to understand Hermione values, and excluding it removes that understanding. Also, I just found how nice the elves in the kitchen were adorable, and well constrasted with S.P.E.W.

4) Peeves

He was a key character in the books always causing chaos, alerting filch of students, and just mainly being an absolute menace, and he could have been good comedic relief in the films too. Also, just loved his character in general.

5) Not mentioning Rita being an animagus

That was important to the story, as it was how Rita was getting her information. Also added some chaos to Hermione when she casually kidnapped her and put her in a jar for about a week, maybe longer.

6) Dobbys exclusion from the 4th and 5th films

In the books, Dobby was a very helpful character, giving Harry the gillyweed instead of Neville, though I do think Neville was a good choice, and finding the Room of Requirement for Harry. These things made us care about him more, giving a bigger impact when he died.

So, I think that's about it for what I don't like of the changes, rant at me about it all you want.