College prospects can be advised as to whether or not it is in their best interests to enter the NFL draft in a given year, or to stay in college for another season. Nobody can make them comply, however, whether it turns out to have been a mistake or not.
The Pittsburgh Steelers are among those who held the belief that Dwayne Haskins was not ready when he declared for the 2019 NFL Draft following an excellent season as the Ohio State quarterback. The fact that he only lasted two seasons with the team that drafted him would seem to justify that.