SCIAG No, I was against them being sent out on loan in the first place!
Thing is though, that it works for some, and doesn't for others. So - Hector benefitted enormously from being out on loan at Aberdeen. Jake Cooper suffered through not going out on loan.
It's all a gamble.
You can just as equally wreck a player's career by keeping him at the club, playing U21s, and the occasional 15 minute run-out, as by sending him out on loan to a club where he doesn't settle, is never played in the correct position, there's a change of manager and the new one's a nutcase.
I think I'd prefer to send them out unless they are good enough to get more than the occasional run-out. If they're not playing regularly in "real" football, they aren't developing as they should.
As well as a responsibility to the club, the academy has a responsibility to the players. Sending them out on loan is giving them a feel for what it would be like to be a professional player, rather than sheltering them in the academy. It's real life. If they're not good enough to at least make the bench at 20/21 (probably older for goalkeepers), it's not right to keep them in-house, it's stunting their growth as adults as well as footballers.