It was never about picking 22 and keeping them all together.
I don't see movement as a problem if instigated by parents or players. There are many reasons to move on when striving at the higher end of sport.
If kids prefer to stay with mates great. If those mates prefer to seek different coaches, players, experiences, great.
My main problem is a few clubs taking the current best to create a lopsided and often a product that wont help players develop because there's no greater opposition. But I see that happening less as more players are developing greater skills. The current 12s is a good example.