Here's an NYT article on what may be a push by casting directors and filmmakers toward a less synthetic look among women, whether stars or extras. I assume this trend isn't one of those fake ones that the NYT feature writers cook up just to draw an audience and generate buzz. Those pretend to talk about national trends among common people, and they just don't have the resources to conduct all the necessary research. Even their more qualitative approaches consist mostly of interviewing their their elite social circle in the tri-state area. But those who drive Hollywood are few and geographically concentrated, and usually willing to talk about where things are going.
On the one hand, a greater emphasis on natural looks will select for those with greater natural beauty and hence better genes -- and no amount of plastic surgery can match that. Right now you can't really alter the geometry of your skull, and that's just as important as the softer features that can be tinkered with.
On the other hand, good genes are in incredibly short supply, so unless Hollywood wants only one or two actresses to play all females roles, from lead down to extras, they'll have to draw from the other group with naturally good looks -- young girls. In Fast Times at Ridgemont High, Phoebe Cates and Jennifer Jason Leigh did not need any work done because they were 18 and 20 years old. Jennifer Beals didn't need a facelift to star in Flashdance because she was 19. Brooke Shields was 14 in The Blue Lagoon. Really the only older sex symbol from youth-oriented movies is Kelly LeBrock who played the Frankenbabe in Weird Science. Mature, savvy, and cool-headed, she provided a good contrast for the juvenile dorks who created her. And how old was this icon of wisdom and stoicism? -- 25.
That's what used to pass for "no longer young," whereas the NYT article says that people now find it disturbing how "young" some of the plastic surgery women are, using a 23 year-old as an example. That's hardly old, but sorry, that's not exactly young either. This mindset is what has given us an older set of sex symbols, contrary to all the whining you hear from aging women (and dickless white knight males) about the culture's obsession with youth. The culture has never been so free of adolescent and young adult influence -- everything is made for middle-aged adults (those of childrearing age and older) or pre-pubescent children.
With all this pressure of the zeitgeist bearing down on them, Hollywood is just not going to go there with young girls. So, the result will be worse-looking women in movies -- we'll get a handful of naturally beautiful ones, but without the ace-in-the-hole of plastic surgery or sheer youth, the majority of actresses aren't going to spin any heads.