I thought the same thing, but apparently the pace in the 80s was pretty close to now. I feel like there is much more movement on defense for the people that actually play defense. I don't necessarily know that any of that cancels out the fewer back to backs, better healthcare, and improved travel accommodations. Also, the game itself seems to stop a lot more with all the replays and other quirks. So while the players might move around more when the action is on, it does seem like they get to rest more in the game.
On topic, I think the average skill level is higher now. Back in the day, being a goon was actually a common role. Those dudes wouldn't even make it into the league now, so that kinda raises the skill level by default. That said, at the higher levels, I don't think there is a big difference. Top players have more range now than they did before, but, at the same time, have basically completely lost some skills (e.g., playing in the post). Defense is a mixed bag too. You have some great defenders now, but a lot of the top players these days don't play any defense. That wasn't really common back in the day. Jokic is considered the best in the world, and he's a poor defender at best. I can't think of an era where the top guy was that deficient on one side of the ball.
