Unfotunately, and I say that because I used to love lifting heavy, I don't think the amount of weight used is as critical as how hard you actually push the muscle. Now maybe this is partly because I went heavy when I was younger but I've lost all that size and gained it back several times, each time using less weight and better technique. I'm actually probably pushing further into the painzone now than I ever have, but the weights are like 60% as heavy, the form is perfect, and the reps are 8-15 (usually 12-15 on heavy compound movements). If I could do it all over, I think I would have tried to go lighter and push harder, and I think the longevity that would buy me would be superior for overall results in the long run.
Ultimately, I think the current generation is obsessed with "looking cool" while in the gym, the highest insult to a millennial is to call them a "try-hard." No one wants to go too hard in the gym. I see what looks like this in even "hardcore" bodybuilders sometimes (i.e. no one wants to be caught grunting in the gym or sweating for that matter).
And heavy/light is all relative. Remember Ronnie actually trained light, for him. 10 reps on everything, all that powerlifting stuff was rarely done later in his career, mainly just for the camera. If you watch Ronnie get 10 reps with those 200lb dumbbells, he is solid as a rock and probably stopped a couple reps short of "balls to the wall" failure. I've seen several IFBB pros doing that same thing with the 200 or lighter, they are struggling like crazy and shaking all over the place.