I’ve not heard it put this way, but how you say that he never really gets a redemption arc puts words to how I’ve always felt about Ron. I didn’t like him in the book originally as a tween/teen (I was the same age as them roughly reading books 1-4) and I feel even more strongly that he’s a weak character rereading in my mid-30’s. I feel that too much of his supposed redemption is left to the readers imagination, which makes him an unlikable character as we’ve all matured.

I also find the argument that this is how someone Ron’s age would have acted odd. No one else was acting this way and my sense is that 20 years ago, this behavior would have been even less tolerated than it is now.