Society has an age discrimination issue. Most of us, even women, would rather look at a fresh-faced young girl than at a woman with lines on her face.
Whatever issues society has, it doesn't follow that a movie producer has to indulge them because of some unsupported delusion that people won't pay to see a quality actress in an age appropriate role. Or a black actor. Or an asian one. Frankly I think there is a lot of credibility to the argument that a movie with some integrity would be more likely to attract fans than a movie that plunks whatever starlet-of-the-month into the role regardless of what it does to the movie.
Is it even possible to fix the problem of age bias in Hollywood, and if so, would that actually help address the problem of age discrimination in society?
Given that they are the image makers it would be a darn good place to start. Is it possible to fix? Maybe. Won't be easy though. The key would be proving that age discrimination is actually harmful to the economic outcome for a film. Challenging case to make since they don't let a lot of people who aren't white and young (if women) into movies to test the theory.