McDavid is on another level then the habs players, but he can still have room to grow or regress.
I think sub 25 year old players are still young guys and can still grow(positive or negative) during that time.
But it goes to my point, good players will overcome regardless of the coach, as seen by those habs players who all played great hockey under MT. Coach doesn't really have that much of an influence unless they are fringe guys like a DD. McDavid would be McDavid under MT, Kucherov would be Kucherov under MT. PK was PK under MT, Max was Max under MT. Coaching on development is overrated.
A Weise or a DD wouldn't be what they were under different coaches, but they are fringe guys anyways who only give you a few good years and then fall off.
Yes, superstars and elite players are going to get there. How they refine their game though, that will be on their coaches. The lesser the player the more influence a coach can have on him.
Nobody ever argued Weise should become Ovechkin under better coaching, or that PK turns into MAB.
From what I read, it seems the people who overrate coaching are the same ones claiming it to be overrated. They have this idea that other posters think a coach is supposed to transform a decent player in to a star one. Nobody ever suggested that, as far as I know.
You expect players to refine their game and have small improvements that when all added make those players better. MT didn't help Subban, the guy seemingly hated how he played and one can argue he was the main reason by the trade. Max became a boring perimeter player, although his two way game did improve under MT, you can give him some credit for that. The others...Gallagher is playing as he did in the juniors and minors, his game hasn't developped into anything different than what it's always been outside the natural filling out of age. Galchenyuk, same thing, not much improvement in his game from his rookie year outside natural progress.
Those are telling signs of what bad coaching is.
Just because he doesn't completely ruin these players rendering them useless doesn't mean coaching doesn't have a big impact or is overrated.