Why are we forsaking that in favor of a "you
don't have to try so hard, it's ok to be
mediocre" mindset?
One reason many feel is the fact that being "the best" often just means making some crappy corporation richer; when you start to feel that the whole system kind of sucks it gets harder to care about accomplishing things within it.
I grew up wanting to be a game developer, but what would that mean in a practical sense? Working 80 hours a week and at the end of the day I'm just making Microsoft or Activision or somebody richer? Even John Freaking Carmack eventually wound up working for Facebook.
Or going solo, and risking my ability to feed/house myself if things don't work out? Or working 100 hours a week because I'm already working 40-50 at a day job?
Ultimately as we get older those kinds of achievements tend to mean less to us than human connections.
If you hate this kind of thinking and/or feel it's wrong, I'm not here to change your mind. Just mentioning why some feel those kinds of ways.