I first visited China over 25 years ago and the domestic Chinese tourist groups then were a bit painful. As that middle class has grown and they've been able to travel internationally, that fun has spread. Yes, they're pretty obnoxious, but it's more ignorance than intentional.

Certainly not so painful that I'd avoid visiting China though.

Younger Chinese travelling as couples or small groups are much more polite. As you said, within a generation or two, I think the reputation as travellers will improve.