That's what development leagues are for, and that specifically is why you don't make a kid who's not ready for NHL play in NHL. If you need to make such considerations, the player likely isn't NHL-ready and shouldn't be playing. In general, NHL is for winning. And for Devils specifically, as Taylor Hall's on his final year of the contract and they just acquired Subban, they probably don't want to just piss the season away for sheltering and catering to youngsters.
I mean, think about Oilers, that's exactly what they did to ruin Nail Yakupov for example. He wasn't ready so he wasn't able to develop his own game.