Over the years, something I've seen more and more of is this: "She may be famous, but in reality, JK Rowling isn't a very good writer."
Some minor spoilers for all Harry Potter books under the cut (and potentially huge ones in the comments).
We could consider that the Harry Potter series, at least, is about young people. The language and dialogue itself is written on the same level as they are. Harry thinks and speaks the way an eleven year old speaks and thinks in the first book and continues onward as a teenage boy. Readers largely grew with Harry; yes, there were many adult fans, but the vast majority were kids and teens when they first read the books. Therefore, it makes sense that the books seem simplistic now; we're older and realize "Lavender, can I see Uranus?" is no wittier than your average twelve year old boy's body-related joke. We also realize how simplistic some of her rules are, such as all Slytherins being mean. (I can't speak for the writing in JKR's books for older readers, because I haven't read them.)
I will say that there are flaws in her world-building, which I don't think have anything to do with her target audience whatsoever. It's very obvious upon re-reading that JK Rowling made up a lot as she went along. I don't blame her entirely - seven books is a lot, and of course her writing changed over time. It's to be expected. Still, as fun as her callbacks to earlier books are, as well as realizations that someone was mentioned in the first book (most notably Sirius Black), the reason we notice this is because so much was thrown in later. We only hear of or meet most people and concepts when it's relevant to the story; while on one hand, it works for infodump control, it doesn't make sense when you re-read the books and realize Aurors should've at least been mentioned in PoA, if not CoS. That surely Ron should have known the Lovegoods (though they are mentioned in GoF) - it actually made more sense in OoTP, since Luna seemed to be a relatively new friend of Ginny's as well, yet when Luna and her father are invited to Bill and Fleur's wedding, it's suddenly apparent that they're family friends. But should a writer be expected to have everything planned out perfectly, or be able to fit them into earlier works? Don't all longstanding works have odd holes and inaccuracies? Besides, her world-building is incredible, her characters are memorable, and the messages left a deep impact with many young readers who are now young adults.
Then there are her scripts, the play and movie respectively. I've only read the script for The Cursed Child, but from what I heard, it's "less about the story and more about the visual effects." A lot of people have said the same for Fantastic Beasts and Where to Find Them. I don't know that I would classify scripts where the scenery is better than the story as good writing. However, they were also collaborative efforts, and really, script writing and novel writing are so different that I'm not sure it's really fair to judge JK Rowling as a novelist based on her script writing. Not to mention that they were collaborative works.
I do think there are some unfair arguments. I feel that a lot of fans built expectations based on their own fannish experiences, whether comparing the books to other works or writing their own fanfiction; canon tended to go a different direction. I'm not opposed to critiquing how JKR went about that direction, but I don't think it's right to judge her solely based on the fact that hers weren't the stories we wanted them to be. (Besides, there were so many ships in the fandom that she couldn't have possibly pleased everyone.)
The other argument I've seen is less about shipping and more about where Harry Potter is rated on the literary scale. I've heard the argument that "the books are more on par with Stephen King." Except... a lot of people would consider Stephen King a brilliant author. This seems to be a case of YMMV, more so than quality writing per se. If you're looking for a highly intellectual novel rife with allegory and mythical symbolism, it's not going to be Harry Potter. Yet a lot of beloved, classic novels aren't like that. Pride and Prejudice is, at face value, "girl meets guy, guy snarks at girl, girl sulks, guy says he loves girl, girl tells him to GTFO, girl's sister runs off with a shady soldier, guy saves the day, girl marries guy." Much like Harry Potter, it's renowned not for knocking the socks off of every philosophical literary academic, but for being rife with fun characters and wit. That's why I like it. A lot of people don't, but I've never heard anyone call Jane Austen a bad writer. It's more a matter of taste.
I'm just about out of thoughts! What do you guys think? Is JKR an overrated good writer, is she a good middle grade writer (but a sub par writer when you're older), or is she bloody brilliant and everyone who thinks otherwise has the emotional range of a teaspoon?