I don't think that you fully understand the current gap between Saudi league and Budesliga/Ligue 1. Former is ranked somewhere between 50-60 strongest league, which is equivalent of German 3rd league and for that kind of league to come into top 5 you would need an insane amount of money, especially in the country that is not known by its rich football history. Also keep in mind that they don't produce their own quality players (unlike Bundesliga and Ligue 1) which is another big problem.
The Saudi League is more like a show league. They don't seem like they aim to increase the quality of the league much more by starting to grow big names from their youth setup. The only thing they aim is to maintain this show by bringing mostly old stars to make supporters happy. They have oil money and they can easily make way better offers than a European team. This is all about the Saudi League.
The other day, a friend of mine made a resemblance that we all laughed a lot. I do not know if you heard of it but there is a "big3" tournament in basketball where old NBA retired players end up playing basketball there, there was even one scenario where one of the players were asked to come back to NBA for one more season just to fill a role, but at least it happened.
So, there players who are like 38 to 45 end up playing against each other 3vs3 with a backup so players can rest as well. That was a funny thing and it is just half court so they do not run around all that much. My friend said Saudi league is basically big3 of football, where players who should be retiring end up going there and getting money because they have their name, that's it. I loved that, it is very true.