Just because Holtz isn't ready yet, doesn't mean he'll never be ready. Tage Thompson was an AHL guy for his first 4 seasons after being drafted, and then had 8 goals in 38games. Two years later, 7 years after being drafted he's now coming from a 38goal season and pacing for over 60 goals so far. Things change and people develop.
And spare me with your 'but his skating will forever hold him back' bs, his skating is fine he's already taken big steps in that aspect, there's plenty of worse skaters in the league. His timing and hockey iq is not there yet, he needs at least a full (60+ game) season to get comfortable with the tempo and pace. He needs to be more intelligent with his positioning and learn to anticipate where the puck will end up.
Haula has been absolutely atrocious the last few games, so I'd 100% be behind giving Holtz a game or two with Hughes instead of Haula. He needs to play and let him make his mistakes, or he'll never learn. And he needs to play in the role he fits the best.