I'll add a different perspective to this, that of a player. Granted maybe not the norm for millenniums though.
One of my kids first coaches was his travel basketball coach 3rd through 6th grade. He was very demanding. Mistakes were punished by either pushups or running. Some tears shed during practices. He wasn't much better during games. That said they won a lot of games/tournaments over those years. At almost every one they weren't the tallest, or strongest, or most athletic. But they were the most discipline and mentally tough. People would comment on how they had never seen a group of kids that young play with such maturity.
My son took those lessons to hart and still ascribes to them. If the team is playing like crap, or the ref is homering them, and the coach just sits there, he sees that as not caring. He feels that coach isn't committed to the team and in the case of the refs doesn't have their back. So the kid would have been out there running and listening to the coach scream thinking they deserved it.
Someone posted that maybe kids don't hold themselves accountable because the adults around them don't hold themselves accountable. IDK, maybe as adults we make to many excuses for our kids. Maybe adversity shouldn't be a dirty word.