Top European clubs are definitely targeting coaches who have good abilities in building clubs, while the Leverkusen coach has proven that with his current performance. Indeed, Xabi Alobso has had to go through a long process to reach the level he is at now and each coach definitely has different abilities, some of which are different fast, there is also slow, depending on whether the club has a level of patience or not, and if Xabi Alonso decides to leave the club he is currently coaching, he must also be ready to be at a club that has a different level and of course has quite tough demands if Xabi Alonso can't adapt quickly and he will be eliminated like coaches in general because big clubs usually want a fast process.
I agree with you that the decision to leave or stay is a double-edged sword, on the other hand this is an opportunity to change fate and career to a high level, but it all depends on Xabi decision between leaving this zone or staying. and the possible difficulty of finding other opportunities. In my opinion, Xabi should stay longer at Leverkusen to prove that there he really has a big influence on the team's performance, not just luck. Xabi does have the qualities of a great coach. 1 more season with Leverkusen is enough and he can accept the offer.