Rowling 'not being a good writer' is misogynistic trope from TRA's and snobs Or people who read a lot, probably of many different genres and authors, and recognise, and accept, the shortcomings of many of them!
Some of my favourite authors are quite severely lacking in some aspects of writing, but I love them for the bits they are strong on! As I said earlier, Stephen Kng is truly limited, as far as characters go. He relies on, usually internal, monologue and the reader keying inot the sitiations h writes. I can't think of an adult writer who keys into childhood better. But his characters are often stereotypical, prone to do things to fill plot holes!
Recognisng th weakness of an author is not the same as traducing their work... let alone being misgynistic, let alone TRA!
This sort of thing is said by less successful authors, usually much less successful, or even wannabes who have never been published. Or people who have never wanted to write, but read copiously!
It really is normal, acceptable to critique any writer, ones you love, ones you hate, all of them! How else do you find the ones you like?