It’s all relative to what your used to, and every person’s body reacts differently to different workouts. One size does not fit all. My workout today, Tuesday and Sat is a 2 mile run to the gym, a half mile swim and a 2 mile run home. I also do abs and 150 push ups each day. I lift heavy three days a week, run every day doing 5 miles on Sunday and 7 on Monday. I’ll be 60yo in 2 months.
That’s me though. I also trained 40 hours a week when I was training for the Olympics so it’s in my DNA.
I did 5 mile daily runs during my non-Keto years. I had been VERY fat as a kid and I think that creates a different health challenge from folks who either never gain much fat or who don’t gain fat until later in life.
Also had a horse explode under me during a dismount that flung me like a booger and landed back first on a rock. 10 years later, that injury plagues me.
As you say, we are all different. If X doesn’t work for us, it might for someone else. If X doesn’t work for us, we can try Y or Z - until we find what DOES work!