I value a lot your football opinion (unlike the opinion of some clowns in here)
So, this a simple hypothetical question, starting from your correct statement that he is not at the level of managers Barca should be getting:
Let's say we agree that Barca should be getting managers at the level of Arteta, Nagelsman, ETH, and the ones we usually talk about as being elite and only worse than Pep.
Recently I have repeatedly forced people to think how would De Zerbi or Postecoglu have done with the squad Xavi is having. Today I added Arne Slot and Conceicao on that list.
How well would you think Arne Slot or Conceicao, let alone Postecoglu, have fared,
had they come in in Nov. 2021 when Xavi came in, and were handed the exact same squad Xavi has been, player by player??
If you're saying, do I think their football skills are better, yes. Do I think some managers would have done a better job than Xavi by now? Also yes. I like Arteta, Slot and Nagelsmann from your list and think they would do better. However, some highly rated managers wouldn't have, and I'll explain why. My overall conclusion is that there are some improvements available on Xavi out there however he isn't a terrible option for now.
The problem is that this Barca job is also politics. It must be taken into account how toxic the environment was during Valverde and Koeman and the politics that comes with the job plays an important part in your success. Perception is everything in FCB, for the fans and the media, and it can cost you your job.
It's like when Koeman said es lo que hay and that the squad wasn't at the level and got sacked. Then Xavi (due to his reputation and his personality) lobbied the same way and got a lot of investment from club levers.
Or like how Valverde despite getting very good results and nearly going invincible/nearly winning treble (fucked by Amigos) was trashed by fans for a bad playstyle. Today they say football is about results and a win is a win.
This is a huge, historic fan-owned club and as a sad consequence comes with huge amounts of politics and appearances.
Xavi due to his reputation and personality was one of the best placed to navigate it and also to get respect from the players. It should also be remembered that the likes of Koeman, Setien and Valverde all fell eventually due to the amigos being able to turn the club against them. Even during those times likes of Puig not playing was brought up as reasons why they should be sacked. Xavi threw him out quickly after wards.
So basically I would sum up managing here like this, there are two parts, the social and football side of it, and they are both equally as important, if anything, the social side could matter more, it's just the culture of this club. Someone like Arne Slot or Ange can 100% be very successful in a settled environment such as City but I can see them coming here and getting trashed by the media and the board if they start slowly or try to train another play style.
Having said all that, my view is that Xavi is in a footballing sense a much inferior manager to the likes of Pep, Klopp, Arteta, Inzaghi etc, and probably worse in a footballing sense than Arne Slot or Conceicao too. The advantage and the strong points he has is his social side, his ability to win trust from players, get his way, throw out certain players and force his project in, get them to give their all.
Arne Slot in particular is doing one of the best jobs in world football as
@Don Juan Laporta Estruch mentioned in the last page. I think by this time Slot would probably also have won LaLiga and be playing better football at the same time. The same applies to many of the managers you listed.
Xavi for me is B-level in world football terms. He isn't the worst and he gets a lot of unfair slack when his results record is pretty good, however, I don't see him as a manager who could make that final push to say CL glory or to be the best team in the world even given we provide another big budget summer. I believe given time that Arteta, Nagelsmann, Inzaghi etc could be that in a post-Pep era.
Xavi has done a good job rebuilding the organisation and bringing structure back to the dressing room and club, so if we do have future success, he is a big part of it naturally, he laid the foundations. But I think if nothing is won this season, someone else needs to be hired to build on those foundations and to take it to the next level, a world-class level, where we can compete against the best in Europe for titles..