Parallel to this, it's really impressive to see how the average skill level changes in various sports as time passes. Two examples that come to mind are:
1. Chess. Due to lichess and the Internet generally, your average chess player is a lot better informed than people a couple of hundred years ago.
2. DotA2. The average level of play has been steadily increasing over years, to the point where a 2k MMR player now is around the skill of a ~3-4k MMR 5 years ago. Techniques that were considered highly sophisticated when the game was just starting are now considered fundamentals that every player should understand.