Exercise for everyone is a mostly modern concept because people are doing less physical work over time. People who worked 12 hours per day, 5-6 days per week in a factory (for example) probably didn't need or want to go to a gym lol I'm guessing boomer parents had parents that largely fit that bill if they weren't farmers who also busted ass all day.

Expecting a single generation to know that they should have been in a gym is kind of ridiculous, especially considering we didn't really understand a lot about that kind of thing until about middle life for them (and we still don't fully) and it wasn't a thing for their parents/great grandparents. We've made more medical advancement in the last few decades than all of human history combined.

Now some dick can hop online, learn practically anything he wants, and then shit on those who didn't have that ability in the prime years of their lives, which were lived during a largely transitional phase of human life.