The movie isn't even out yet, how is it doing poorly?
Regardless of that, the quote she gave is pretty racist/sexist. Movie's are for everyone. Perhaps it is not the targeted audience, but that doesn't make it ok to belittle or invalidate someone's opinion of something. Also, note she said she didn't want to hear what didn't make it work. So, only negative opinions from 40 year old white men are unwelcome, but if they are positive then that's ok? It's a messed up thing to say either way.
Imagine this being the other way. Let's say a new movie about football comes out that is really "masculine", but it's not great. One of the male stars says "I don't want to hear what some 40 year old woman has to say about what doesn't work in this movie. It wasn't made for you!" or "I don't want to hear what some 40 year old homosexual has to say about what doesn't work in this movie. It wasn't made for you!". See the problem? If you swap the race, gender, or sexuality in a statement and it automatically becomes problematic, then the statement was problematic to begin with.