It's too bad age is a factor when it comes to casting. Patrick Stewart was in his late forties and early fifties during TNG. So I don't know why age (within reason) would be a big deal. So as long as the actor isn't being followed by someone with a dirt and shovel then don't worry about age.
They need a young actor who can land on a mat 50 times a day. Someone who can run and run and run.
Plus all the other physical things the new doctor actors have to deal with.
In the TNG Picard would just sit in his chair and say "Engage"
Not very demanding.
Then we had the movies and they turned him into an action hero