Most people don't realize that TOI distribution. I think they actually produced reasonably fine for their age at 5v5, and the expectation for them at 21-22 shouldn't be that they have to outproduce a star player like Zibanejad at even strength or they are busts, even if their draft billing said they could by now. It's not that black and white. They could close the gap even more next year.
The issue is their overall point totals stink because they don't get quality PP time. There's no question it has a major effect on their confidence, which can also have a negative impact on 5v5 play when they have to deal with "35 point 3rd line bust" labels all year and offseason. It feels like the team is at a crossroads where they need to either commit to these guys with legitimate PP opportunity, or just trade them. Preferably the former because I don't believe the current core is a couple of tweaks in the support players away from a Cup. It's a waste of time and we might as well see what happens committing to the kids for a spell instead, then adjust accordingly next summer.