Football is not a meritocracy where the best end up at the top no matter what.
Getting a chance at the right time or becoming disenchanted because you dont, or getting sent on a bad loan can permanently change someone's career trajectory.
Look at Chelsea right now. Opportunity. If Chelsea didn't have a transfer ban we'd most likely be seeing Mason Mount, Reece James and Abraham on another loan to another Championship side, and people would go 'they're clearly not ready'. As it is, they're not there. They're at Chelsea, and they're showing exactly how good they can be with a little luck, plenty of talent and the right chance at the right time. It's a funny old game. One minute you can be a good Championship player because someone didn't take a chance on you, the next you can be starring for England in a team in the top 4...
Bersant Celina is no less technically talented than Mason Mount for example. If anything he's probably more naturally gifted. But he's kinda stuck at Swansea. Weirdly, if he was in the Eredivise last season he'd probably have been afforded more chances to express himself, he probably would have and he'd probably be wanted by a Premier League club right now. Football hey?
Obviously i'm not saying we should stop signing great players and just randomly throw kids in... i'm just pointing out what @domalino argued correctly. The cream doesn't always rise to the top. We could absolutely waste a tonne of potential by not giving them the right exposure to elite level of football when they need it.