It's not the "allowed looks" as much as the fact that they must be all super-fit and super-beautiful, which inevitably makes it look all samey. The young Al Pacino or Dustin Hoffmann wouldn't get roles today, because they're not conventionally attractive. Tom Cruise is particularly guilty of overcasting beautiful people in his recent movies, but he's hardly the only one doing that.
The last leading man that I can remember with non-conventional looks, is Vin Diesel - and he got there by muscling (eh) his way in, not by acting.
Every era has its tropes, and this one may be slightly stronger or you are just not liking it so much, thus seeing it everywhere. Look at some mainstream movies from ie 60s, all people wearing same clothes (all guys wearing suits and shirts for every single activity, surreal now yet even my own grandpa was working (biggish) garden in nicely ironed shirt and pants every day). Everybody is nicely shaven, same haircut, same... everything.
Hollywood was never about matching reality, rather just creation/working on dreams, so one shouldn't expect these things. If you complain, you basically complain about what majority wanted to see at given time, which is never fringe-pleasing experience.
> Tom Cruise is particularly guilty of overcasting beautiful people in his recent movies
It has been years since I followed Scientology, but IIRC its beliefs see physical attractiveness and physical fitness as a sign of moral correctness, therefore anyone without it is suspect.
> Tom Cruise is particularly guilty of overcasting beautiful people in his recent movies
Heh, this can be interpreted in two ways and I think both are true. His movies have too many attractive people (over-cast). Also none of those attractive people are very memorable because they're in Tom Cruise's shadow (overcast).
Definitely attractive, but probably too short/not built enough these days. I doubt Michael J Fox would have been a leading actor today too. Can't decide if Bruce Willis would have made the cut, but I would lean towards not. His roles went to the steroided up Rock/Vin Diesel.
It is not just US cinema though. I see the same in other countries' movie markets such as India's. Possibly just that population increase of potential actors made it more competitive, so minimum standards increased.
The last leading man that I can remember with non-conventional looks, is Vin Diesel - and he got there by muscling (eh) his way in, not by acting.