Because he's already been playing on a constant high level in those 4 years, especially considering his age. A level Pjaca has yet to reach, being only one year younger.
I would argue he needs to join a better team to improve even further, and now that we finally play a formation that makes use of wingers, i'm confident he'll do so in summer.
Are you really mad at a young winger because he wasn't overly eager to join a team that used to play 352? Having the Coman case right in front of his nose?
He was 20/21 and had (and still has) plenty of time to grow, nothing wrong in staying another year at Sass, plaing in europe with your team, and waiting how things turn out at Juventus, formation wise. Looking at how things stand it was the right thing to do.
WHen he was turing 19, i was expecting alot and highly anticipating. 3 years later, its still the same.
Why do we rate Berardi ? In 4 years time, his technique, vision, passing, athleticism, improved nothing at all. He's still incredibly inconsistant.
This is juventus. What can he offer ? He's fast but thats it. His technique is decent and his dribbeling is modest. He wont break open the game against amazing sides with brilliant dribbels. He doesnt have remarcable vision or passing or shooting.
In 8 years time, he's still the same player just more matured. He'll still score the same goals in serie a. He'll be the new Candreva. Candrava, is an Inter player and suits well there.
Pjaca, unlike Berardi, has great technique and remarcable good dribbeling. He has great vision in where the run when and he'll only develop from this point on. He showed against spain what potential he has. He came in against Porto made a fine run (Dybala should have send the pass through where he was without needing a deflection cause he wanted to pass to licht), and he scored an exquisite finish
In a few years time (or faster) , Pjaca will be a horrible player to play against, turning defences inside out and having a proven technical good shot
Berardi started at a good level aged 18, and wont improve
Pjaca was not as good when he was the same age, but he'll become a vastly superior player to what Berardi will ever be.