If your expectations were McDavid, Crosby level production, then yeah he has disappointed, not close to their rookie or sophomore seasons
That being said, he still has the 3rd highest PPG among 18 year old active NHL players, only below Crosby and McDavid.
Even his 19 year old season ranks 5th best PPG among active players. Also below Stamkos and Svechnikov...
But really, people have to realize development isn't linear..
Laine had one of the best 18 year old seasons. Produced at a similar clip to Bedard and Celebrini in a noticeably scoring environment while finishing 7th in goals , didn't exactly pan out as a superstar.
Mackinnon's rookie season production is identical to Jeff Skinner and produced at a lower clip than Ryan Nugent Hopkins..
Neither of those players are in the same stratosphere as MacKinnon now.
Kucherov didn't become a star player until he was 23.
And the list goes on..
Maybe he doesn't pan out as one would hope, but ragging on his current NHL output so far is silly. He's objectively been one of the best in his age group, even if it's not quite the level you expected relative to hype