Do you consider Within Temptation as an example of genre change done right?
Maybe it's just me, but I got into Within Temptation by basically re-discovering Nightwish and then falling down the seemingly neverending (mostly female fronted) metal rabbit hole. But I also usually have quite selective music tastes that require significant differences between 2 bands to be equally enjoyable for me. Within Temptation partially fails at this front because their most distinctive of their first 4 albums is The Silent Force and is hence my favorite of the 4. But that's likely just my personal take.
In any case, while many metalheads will say that their latter 4 albums have been trending downhill, I think that their shift is done right. While it can be largely described as generic alternative metal with with some metalcore and djenty elements, they're retaining strong symphonic flavor and Sharon's passionate vocals and bombastic elements make their music quite distinctive and not as generic as whatever generic alternative American band.