“Actress” also still exists, but many women in that business prefer “actor” and it is becoming a default.

Yep, I'm aware. They've gone back and forth on that though in Hollywood, not sure where they landed currently on that. The last Academy Awards was still using actress.

The existence of a word doesn’t change the fact that language is fluid.

The fluidity has nothing to do with the existence of a single word or not, but about human nature, and it's error rate/drift, and how all humans can't "stay on the same page" over a long period of time about the rules of a language, so the language morphs over time. Lol, basically 'cancer' for languages.

But we should try, so that we can maximize the ability to communicate with each other.