This is what always happens. People will pencil some prospect in as an instant stud in the NHL because they looked good at a prospect camp or did really well at an easier level, like they are doing now with Fox and Kravtsov. Then when that player goes through some growing pains adjusting to the toughest hockey league in the world before they're old enough to legally have a drink, people will decide they are a bust, like they are doing now with Lias and Chytil. Then even if the player turns into a good NHL player who can fill a key role at a young age, people will want to trade them because they assume that some new prospect who is barely scoring more in a junior league than the developed player has in the NHL is going to be way better, like they're doing with Skjei.
Prospect development is an uneven process that takes time and only infrequently results in players who are perennial all-stars and surefire hall-of-famers, so just be patient and have reasonable expectations.