Supporting young players is important because the older ones will soon retire. Making such laws to promote young Italian players is cool. Young Italian players should not depend on the Italian league alone. I am sure that some countries would be pleased to hire talented players from Italy. Football agents would have to look beyond the Serie A for clubs for their clients.
It should be like that, Donnarumma is an example of how he grew with AC Milan. Because at that time there was trust from the Milan coach to make him the main goalkeeper. His performance continued to grow and he was called up by the Italian national team, getting a lot of input from Buffon in PSG, made him better. If all clubs were like that, Italy might have had more talented young players in all positions. It's just how the club gives them the opportunity to play.