Sitting out is pretty much required now because of the style of basketball that’s played. In the past the area of play is much smaller, where the three point line is pretty much the limit of the area you have to guard. Nowadays the limit is up to 30, 35 feet out, depending on the team you are playing.
Also, the step backs, side steps, eurosteps, slow steps, quick stops and all of that is killing the players knees and backs. Previously most of that herky jerky action is mostly by the defence, and the starts and stops aren’t even as tough as the offence today.
Some of these moves are not allowed in years past. Those gather steps, offensive fouls, illegal screens help with the scoring but absolutely put a strain on the defenders body.
If the nba wants to stop this, take out all the illegal moves and it can solve maybe 30% of the problem, call illegal screens and that’s another 30% of the problem.