Not a single woman mentioned thus far, I note (with the possible exception of Caitlyn Jenner). I can’t think of many that have changed dramatically over the years for reasons other than plastic surgery.
That said, Renee Zellweger is all over the map looks-wise - some of that is surgery, some of that is exercise and dieting, and some of that is aging.
Wilmer Valderrama, who played the fey, pixie-ish Fez on That 70s Show, and then hit the gym for a few years to play the hulked-out generic tough guy cop Nick Torres on NCIS.
Jennifer Lopez, on Shades of Blue, is scarcely recognizable as the youngster who played Selena back in the 90s. And Elias Koteas has sure changed from Teenage Mutant Ninja Turtles to Chicago Blue.
Frank Langella was heart-throb handsome in Mel Brooks’ the Twelve Chairs, and as Dracula onstage in the 1970s and in the 1979 film Dracula adapted from it.
We all get older and grayer, of course, but when Frank Langella shaved his hair real short and started taking rock-hard serious roles it changed him completely. I don’t think I’ve seen him smile in ages
A guy I knew as a grad student followed the same route – long-haired Bohemian appearance when young, now close-cropped gray hair and no smile.
We seem to do these threads about every six months and I have some of the same issues every time.
While the OPs question is indeed a broad one, are we really surprised that someone (Diana Rigg in this case) looks a lot different at 75 than she did at 23?