When I started rock climbing, 25ish years ago, climbing gyms were in their infancy. People learned outside, slept in the dirt, and got the miles in.
Now, without exception, elite young guns have a gym background. Elite old guns train bi weekly in the gym except for road trips. The average ability level, especially on safer stuff, has drastically moved up.
I'm sure there is some truth to this among cyclists. I remember starting in March and racing myself into shape. Once I had 10-12 races under my belt for the year, I started getting fast. Now there is some Zwift monster in mid season form in March. It allows people to skip less desirable events and theget the same training effect in their basement. It changes the whole dynamic of racing among the employed.