Germany has over 60% foreign players in the Bundesliga.Likewise for the Italian, Portuguese and Belgian leagues.
The Spanish only have about 45%, but the best players in La Liga are the foreigners, so that number will continue to rise.

I expect the percentage of foreign players to reach 80% in the next 25 years. If you want to keep competitiveness.
Else, you can impose rules like stupid countries do, limit foreign players and think that you're helping your own national team by doing so.
You're not. The Belgians have had the best national team development in Europe. Foreign players, as role models, only help bring more children from a country towards professional football.

So, if most of the european leagues have a higher percentage of foreigners playing in their leagues than they do home grown players, then doesn't that mean that most home grown players are playing abroad regardless of which country they come from?