I had a nostalgic re-read earlier in lockdown, now I'm on a nostalgic re-watch.
But they went downhill after the first two didn't they?
The uniform swapped from being nice to being cheap black jumpers and they all looked long-haired and scruffy (some of that is being teenagers in the 2000s I know!), they chopped and changed the plots so much, and without John Williams the music just wasn't as themed/good.
There are some nice little extra bits (the animal sweets in their dorm, McGonagall teaching them to dance in GoF for example), but in general they're just not as good as the books. I'm also turning into my DM and hate the fact that half the action seems to take place in the gloom — even Hogwarts looks dark and miserable!
They just seem to lose some of the magic from the first couple (which I thought Fantastic Beasts managed to re-capture well in the first one actually). I know the storylines became darker and more grown up, but the films seem to take that to the extreme.