Why do people care about his height? Your weight matters way more than your height in hockey. The difference between someone who is 5'8 rather than 5'11 is a lot smaller than someone who weighs 170lbs vs 190lbs.
Gaudreau, St. Louis, Gerbe, DD, Gallagher, Marchand, Tootoo, etc have shown that smaller guys can play in the NHL. The thing that all of these guys have in common besides height is their weight which is more than sufficient to play in the NHL.
The only thing height really effects is someone's reach imo. But how much more reach does someone who is 5'11 have vs. someone who is 5'8? I don't believe it's that significant.
As long as DeBrincat can play at a healthy weight for the NHL, there's no reason why he can't be a successful NHL player