I think the narrative in Harry Potter is fine but the more I think about the magic system the stupider the movies seem to become.

You can boil this down to one simple factor, it creates tension based battles using soft magic. Spoilers and I have to wonder why the hell that's happening. This has never been explained, and the best I can do is assume it's based on willpower or something, but why do they clash, why do they move? I have too many questions about scenes like this to continue taking it seriously.

I think HP needed to establish its magic properly if it was going to use battles involving it in to create any sense of tension, but it's very hard to invest in these conflicts when there is no knowledge of a cap or a limit.