I think those points both have merit. I grew up on a farm and my dad is 72 and still farming. You are exactly correct about laborers not physically being able to work 50 years at those jobs. As his kids grew up and moved away from the farm, he had to buy more things to help do the daily things needed and had to hire help and things that he tried to do himself took longer.
But from the numbers point of view, back when Social Security started, the average lifespan was 10 years shorter so from a purely mathematical standpoint, there’s not enough money coming in to pay what’s going on right now since people are living so much longer.
Whoever mentioned that they should put the money back they keep taking from that fund, that would help too, or maybe some other type of percentage based payout, depending on how old you are when you start taking it out.