The issues he had last year were fundamental issues. Those get fixed over time and developing properly. They did the best thing with him this season. If he was ready, they wouldn’t have spent money during the off-season.
Let him marinate and give him some games late this season, to see where he’s at. When he’s able to play important NHL minutes consistently, he’ll stay in the NHL. That doesn’t mean minutes with major protection and struggling either.
The worst part about these kids complaining is, in the grand scheme of things, it’s such a small time frame, but the good that comes from it, will last a decade. Ask Edvinsson and Clarke about their extra AHL time last year. Guarantee they say it’s contributed to their success this year. Edvinsson plays 20+ minutes a night with no protection at all, and is well on his way to being something special.
The NHL just isn’t a developmental league. When these kids play too early, rarely does their game ever round out. They end up always having issues (mostly) defensively. It’s 50-80 games of extra development in someone like Nemec’s case. He’ll be much better for it though.