I'm not saying it's true 100% of the time, but I've noticed that older movies tend to have more fat and when they do it's more egregious.
Throughout this discussion I've realized that this whole conversation is fraught with survivorship bias - we imagine generic marvel movies or the fast and the furious stuff when we think of modern movies, but when we think of the past we really only consider the classics. We haven't yet seen what modern movies will qualify as classic.
The 80/20 rule holds here: 80% of everything is crap. That applies to movies now, and it also applies to movies in the past.
There's also the very real thing of changing tastes. Movies are made to appeal to the taste of audiences in the time they're made. Modern tastes are different than the tastes of yesteryear.
I think it's not right to say that modern tastes are better or worse than older ones. They're just different -- but it makes sense that the ones aimed at different tastes will be a less popular.
Sometimes those scenes are fat. Poorly made movies are certainly not just a modern phenomenon.
But sometimes it's critical that those scenes are as they are.