The only problem is how long saudi can only rely with the money to help the club gets demand by recruiting european players? we have seen that many times that if this is not fully worked. You can see that some players have been trying to exodus back again to the european competition.
This is also destroying the reputation of the league as well as there would be some bad reviews about this, i think that this can become the consequence when you were hiring people caused by money. They were not willing to play in this league but they came due to the money.
So, we can take this as the main evaluation to consider whether it was successful or not.
This is why I believe that loaning should start being something that actually matters. There are so many players who are either young, or who are not getting the minutes they want to get at European clubs. Clubs can't sell them because those players salaries are high, and the players do not want to leave to get paid less, but also the players do not want to be sold to Saudi clubs for good neither, they want to maybe come back.
This means, Saudis could get young players or unwanted players on loan, for a year or even half a year, and then they could just make them play. The players who show great promise will end up with another career at Europe and just go back, and the ones who fail, will not be wanted for good this time.