As far as judging Pep goes, he is the managerial equivalent of Messi and Ronaldo these days. That is, scoring "only" 20-30 goals is considered a failure, or a disappointment. Remember 1-2 years ago people were blaming UEFA and calling it shameful that Messi was even in top 3 for Ballon D'Or? We had some of those clowns on here, too. All sorts of justifications were thrown in. What would be called a brilliant season for any player (see Griezmann this season) is a failure for Ronaldo and Messi. So Pep is there, among managers.
He is harshly judged. Extremely harshly. It turns out, everywhere he goes, things are perfectly ready for winning trebles year after year. And if he doesn't do that, it is a failure. Forgetting the fact that he is probably the youngest 2 time CL winner in the history, and had he won another, would equal the record too, again, at the youngest age.
I am almost certain that if he goes to ManCity and wins Premiership year after year, people will be saying "yeah, but ManCity had the best squad in the league anyways, and they had funds to bankroll Guardiola's purchases". This is obviously not considering the fact that ManCity had the same situation for the past 3-4 years, and have been terribly inconsistent. But it won't be considered an achievement for some. The same is true for Bayern and Ancelotti. Pep's Bundesliga wins and CL semis exits are said to be a failure by some, but even if Ancelotti fails to achieve that, there will be excuses. Ancelotti fecking lost the league title to Montpellier as a PSG manager, lost a huge lead in Spanish league to Atletico and Barca, got knocked out of CL many times. But he is immune from the same criticism, because apparently Real Madrid and PSG are underdogs.
Anyway, people who criticize him are too harsh, and they won't bother applying the same standards to any other manager in the world. Because if they do, just about everybody is coming out worse than Pep. Take Simeone, he deserves the best manager title right now. But it is one thing to be an underdog and play as an underdog, and a completely different thing to be a favorite and play as a favorite. Not many managers can make the transition. Mourinho couldn't at Real Madrid. Him trying to push the idea that Madrid are poor little shitty club didn't find support at Madrid in the end. In football, the results are the king, but a bit of perspective is necessary when judging. Simeone doesn't have the best squad in his hand, but give him (or Mourinho) the best squad, be it Madrid, Barca or Bayern, and he won't produce a good footballing side. It will still be negative underdog stuff.