We obviously need a core of Italian players, but you also need those foreign star players that fans the world over can identify with. Players like Dybala, James, Pogba, and the like sell jerseys and attract new followers, ultimately leading to more money in the club coffers.
No one supports a club because they have savvy management, an awesome stadium, or sound financials.
I started supporting Juventus because of my best friend in school, Mauro Italiano. He gave me a Juventus poster, and then I witnessed the awesomeness of Baggio. My dad had already been a Milan fan, and with his influence and the Dutch triumvirate, I could have easily opted for the red and black stripes, but I definitely made the right choice. Baggio made me fall in love with football; he made me cry in that 94 World Cup. When I found out he was playing for Juventus, it concertized and cemented my belief in that team. A year later we won Serie A, and in 96 we won the CL. What I'm trying to say is, that unless you are born in Italy in a die-hard hardcore Juventus family, nothing is forcing you to choose Juventus. Kids grow up watching Messi and Ronaldo, and they identify with them, thus supporting Barca and Real Madrid respectively. When we had Zidane, Del Piero, and Davids, teams feared us, and we were considered the best in Europe. It's time we returned to being the pinnacle of football, and to do that, we must make key signings, while retaining our best players, NOT selling them.