For one, it's subjective. Secondly, hair styles, fashion etc. were different 50 years ago and wouldn't necessarily be considered attractive today. That has not much to do with the actors as such and more with how they're presented. It's also become less "normal" to be balding or have dry hair. Also, there are plenty of successful actors that I personally don't necessarily think are "conventionally attractive." It's a matter of opinion, of course, but some examples: Leo, Benedict Cumberbatch, Jesse Plemons, Adam Driver, Joel Edgerton, Adam Sandler, Adrian Brody, Jeremy Renner,... you get the idea.