Like NBA I don't understand how guys rip their shoulders, break their ankles and knees, and 2 weeks later they come back on the court.
There is undoubtedly more doping, but also a work ethic 100 times greater. LBJ, 38, who shines in a much more physical sport while a footballer who plays at 33 becomes a feat.
NBA is not a good example. Right now they are heavily criticised for load management, meaning sitting out games just for rest alot, not even injury, or faking injury or sickness to recover or rest more. Granted they have way more hectic schedule, double back to back games sometimes (3 games in 4 days etc).
Its a very physical high tempo twitch and turn short bursts sport that leads to more injuries, despite the rolling substitution method. So players get more injured now then before due to raised tempo then before.
But still they are also way more pampered and coddled by their organisations more then before by sitting out so many games. Health is more important, so generally they last longer nowadays.
LeBron is a freak, he is not a norm but an exception. NBA players in general are athletic and physical anomalies compared to general populace.
But no way would they be able to withstand as long careers in football, simple because football is an endurance sport, about lasting active 90 minutes with alot of running that requires peak lasting conditioning, a single game is very demanding. Stamina more key then short burst insane athleticism or jumps, reach like in NBA. Athleticism and preparation is way higher in NBA and NFL but demands are way different too.
NFL are physically monsters, but they should never be used as a good example. They legit abuse and maim alot of their players for life.