Before Pep took over at Barcelona they had one la Liga twice in the previous 10 years, the Championship League once in the previous 30 years, no Copa del Rey wins for 10 years.
The next 4 seasons saw 3 last Liga titles, 2 Champions Leagues, 2 Copa del Reys, 3 Spanish super cups, 2 UEFA super cups and 2 FIFA club world cups. He took Barcelona from a club in Real Madrids shadow to the best club team in the world. Yes, Bayern Munich were dominant before and after his time but he maintained their record despite some doubts about whether he could succeed outside of Spain. And Man City have had loads of money thrown at them, but that hasn't guaranteed success for them or anyone else before. But he has overseen 5 PL titles, 2 FA cups, 4 league cups and a Championships League that they were unlucky not to win over the last couple of years.
Pep is undoubtedly a brilliant coach, arguably the best in the world over the last 15 years or so. Not only winning, but playing a fantastic brand of football along the way. Of course having players like de Bruyne and Haaland helps, but there is also the work that he has done with players like John Stones who has gone from an almost joke of a centre half to an incredibly influential player.
You can question the financial side of Man City and their owners, but it's a little churlish to not acknowledge the impact Pep has had in the game.