Still, we'd probably have more of that type today if masculinity hadn't fallen out of favor in the popular culture.
Absolutely. The first wave of those guys were GIs who got back from the war and then went to acting schools under the GI Bill--Marvin, Ryan, Jack Palance, etc. The second wave, like McQueen and Eastwood, were a little younger, but still not baby-boomers.
Still, we'd probably have more of that type today if masculinity hadn't fallen out of favor in the popular culture.
That, and I think that if you are a masculine man, acting isn't something that appeals as a career choice the way I think it once must have. Finally, I think that the fact that Hollywood largely stopped making those kinds of movies in the 1980s, focusing on capturing teen audiences rather than adult audiences played a role.