i've read the entire thing and i completely disagree with you. like the other guy said, tolkien pioneered the genre. the way all those mythical creatures are described in today's fantasy works are greatly influenced by his take on it. he might not have invented them but he made fantasy mainstream. harry potter's greatest innovation imo is that the whole magical world coexists side by side with the regular world. the diagon alley and the 3/4 was probably the coolest parts for me as a kid. the idea might not be novel either, but it was executed really well.
when it comes to comparing the universes harry potter shouldn't be even mentioned in the same category with tolkien. tolkien tried to describe every little detail of his world, and probably would if he didn't die before finishing the silmarillion. there is the elvish language he created, poems he incorporated into the books, history etc.
what do we really know about harry potter's world? jack shit. 90% of the scenario happens in one place. hardly anything about how magic works is explained. the main villain is a fucking joke. i mean how long does the wizard world exist in harry potter? only now some guy figured out that shuttering his soul will make him unkillable and no one has a clue this is possible? are you serious??? it's a sloppy piece of work.
as for the creativity you mentioned, quidditch was certainly an innovative and cool concept which deserves praise but some of the other aspects were cringe worthy (and i don't usually use the word "cringe") when it came to names. all of the spells are words in latin, some of them changed a bit. avada kedabra...? rly? maybe she should have added hocus pocus or shazam, cuz why not. the names of the houses are extremely plain. griffindor aka griffin (which is also the symbol) aka courage. slytherin aka slither aka snake. imo a really poor job at representing the concept of the house as well because they are supposed to be ambitious and cunning which isn't exactly what snakes / serpents represent in most mythologies unless her sources were nazi propaganda. ravenclaw with a raven's claw as the symbol, fucking genius innovation.
the clothes are as cliche as it gets. hell, mcgonagall looks like a rip off from the magician of oz. long robe, pointy hat. very original. personally i disliked the idea that the wizards are like amish fashion wise, stuck a few hundreds of years behind. i don't remember it being explained either. we are just supposed to assume wizzards are supposed to wear long robes with pointy hats and use magic wands to cast spells. can you get more cliche than that?
i think up to the 3rd book harry potter is probably one of the best fantasy series for kids and should be compared to the hobbit. from the 4th book onward it started to explore mature themes such as romance, dealing with death, despair. the problem is the depiction of the world isn't mature or intricate enough. once you grow out of your teens, in retrospect it's kinda meh.