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.
I recall many nations doing something similar to boost their local squad. Apart from giving citizenship to good players so they can play in the national team, there is countries that imposed for example that the goalkeeper in the domestic league must be a local person. Others imposed a maximum number of foreigners per team in the league, like 3-5 in general, in addition to not allowing lower leagues to have foreign players. Others impose that foreigners cannot play any competition outside of the domestic league and regional competitions.
All these measures are done to boost the squad in the long term and Italy move comes in the same way.