It's a catch 22 situation really. We can say that it's best for a player to stay at Motherwell and look to progress to the first team, but what if that doesn't happen for whatever reason? Injury, loss of form, simply not being good enough.
The example a lot of fans use is Jake Hastie, claiming his move to Rangers wasn't a good move for him. I think his level of performance after that short purple patch for us shows he absolutely made the correct decision.
If he'd stayed at Motherwell he'd likely have shown the kind of form he did when he returned, which would have seen him slide down the pecking order and eventually get released. I don't think him not signing for Rangers would have seen him suddenly become a quality player who then won a big move a few years later.
As things stand, he's playing in League Two. The only difference is he's doing so with a relatively healthy bank balance from his Rangers deal, so he's come out a winner in that regard.