Social learning is what evolves and yes, social learning can evolve really quickly. One generation after another, techniques and teaching get better, especially for unnatural specializations like skating and stickhandling/shooting, on top of physical training which also has evolved. Go look at the training McDavid had as a teen. The previous generations neither had these specific format of training, nor the same set of developed skills (from the previous generation) to draw upon. Stickhandling, shooting and skating techniques of training have all evolved through the generations.
Our evolution as humans, our brains, since we've started to massively neotenize around 80kya, is done in great part through social learning.
Evolution is a lot more complicated than you think. It's not just random mutation and selection. There's more to it than that once we reached a much greater period of social learning. We've massively neotenize to reach the longest juvenile period of all living creatures.
The sport has also evolved, as with the increase of both population pool to draw on and the training, increasing the level of talent you'll find league-wide.