It has destroyed loyalty and has ruined a lot of kids. Most these AAU programs don't do a lot of skill development and just play a lot of games. If you play more games than you practice, you're probably stagnating your growth.
It has also made it so kids feel like the grass is greener. They don't like getting coached hard? The answer is going to another team. They feel like they need to play more? Another team. Not winning enough? Find another team.
It's trash. I hate it.