The person who is right for these jobs are the people who relate most closely to the characters. It's always been that way in films, and no one's ever questioned it. As p.c as it might sound, I've always thought the more diversity the better. Unfortunately, that's probably the area I am least informed about. I don't think that will ever really affect actors.
Nothing can replace actors.
It's human nature to want to relate to real people on the screen. I really think that's what makes or breaks a career. I can't possibly change someone's personality. I tried that once. I had a client who has had a couple of films produced and created several VERY successful comic books.