There is definitely a muscle tissue sparing effect of eating enough protein which can be very helpful for endurance athletes, but I agree that most recommendations are wrong.
1.6-2g per kg of LBM (body weight - bone - body fat) is a general guideline for athletes during moderate training. Example: I’m 156+15% body fat with 7 pounds of bone, so my LBM would be 126lbs/57kg. So I usually shoot for more than 105g of protein if I am running a normal diet.
If I am on a calorie restricted diet, that recommendation moves up to 2.3g/kg, so I shoot for 130g. Not significantly more than normal, and definitely reachable with a normal diet.