A lot of people point out that it doesn’t make any sense that Harry and Ron didn’t like their schoolwork. Well I figured out why:
It’s because the magic system is just as boring in-universe as out of universe. It doesn’t make any sense in universe either. Harry and Ron realised Rowling’s magic system kinda stinks way before we did, because they spent all day learning it.
If Sanderson had been writing Harry Potter, then Harry and Ron would have liked learning magic as much as Hermione did (Also, Sanderson actually DID write a book about a super-school, it’s called Skyward, it’s good)
Stories don’t have to have “hard” magic systems to be good. I’m a big fan of the magical realism popular in Latin American fiction - where the magic is ambiguous and never quite explained at all.
The problem is the way that Rowling uses magic.
Rowling was clearly writing mystery novels, while lifting a lot of ideas for her setting from like The Worst Witch series. She uses magic spells like a Checkhov’s gun kind of thing, usually establishing whatever magical principle will save the day earlier in the novel. With a relatively self contained story, it works really well. Prisoner of Azkaban is one of her stronger books - the way that she sets up the mystery with the time turner as well as the stuff with Sirius Black, etc - because it’s very “clean” in this way. She introduces a bunch of new elements to her world, but they are all tied around supporting her story. This is good writing.
The problem is that Harry Potter books don’t work as an overarching story. It is abundantly clear that the Horcruxes and Deathly Hallows were not planned from the beginning. Rowling got to the last two books, realized that she needed to write some kind of ending, and then completely drove her plot off the rails.
You could say because she didn’t have an established magic system, it made it easier to drive off the rails, but really, it’s more that she’s competent at writing stand alone mystery novels (which really, that’s what books 1-4 are and they’re the best in the series for it) and not larger narratives. She doesn’t know how to convey the scope of a war, she doesn’t know how to tie together an Epic fantasy.