@zuzie their intent is very clear that they want to make SPL even bigger then the Premier League and the La Liga hence I believe that they’ll keep acquiring young and old stars from these two leagues primarily. Furthermore Messi isn’t coming but I won’t be surprised if several young star’s ditch their clubs and move to SPL because they can always return back in a year or two but they won’t get this kind of money elsewhere.
It is impossible for them to make Saudi Professional League as a big league like either La Liga or Premier League. Because you can not have a big league with very old players like Benzema or Cristiano, Kante. Those old players can bring some lessons to domestic players in Saudi but their performances will not be as same as when they were young years ago.
If Saudi Professional League can have players like Mbappe, many of such young super star players, they can increase the league quality a lot. Unfortunately it is impossible to convince players like Mbappe to join the league. They will want to play in Europe and win Champions League, Ballon d'Or, money is not all they want.
Young players can not grow up to super star players if they only play in Saudi or South America countries like Brazil, Argentina or Uruguay. We all see those youth players try to find their future in Europe. It is impossible to convince youth European players to join Saudi Professional League. They must build the league with their local players and players from Middle East nations.