While I’m fortunate now to be able to dedicate time to the gym and other physical fitness, this was not always the case.
We lack the societal incentive structure to allow someone working 60-80 hours a week to reduce their workload to physically recover. We do allow that same person to spend 5-10 years income on surgeries which have 4-6 week recovery times.
However, given that people "graduate" their 20s without having done this, then everything you say becomes true, people end up so weak that they have to rebuild even basic core strength and posture. So practically what I suggested is useless except for maybe the next generation.
https://www.bls.gov/charts/american-time-use/emp-by-ftpt-job...
Note how two job holder average is barely above single job holder average. These are probably people working two part time jobs with a 4-5 hour shift each.
How about activities? BLS has some data there.
https://www.bls.gov/charts/american-time-use/activity-by-age...
Note the leisure column.
Screen time average is about 7 hours a day (not the best source I guess compared to say if apple published their data): https://www.demandsage.com/screen-time-statistics/
You could do a lot of good with a 3 day a week 30 min compound lift strength training workout. Deadlifts, squat, bench press, overhead press, pull ups.