Was he even? I guess he could be considered the main purveyor of "Tiki-taka," but that had a shelf life of like a decade at most and can't exactly be considered a staple tactic of the sport. It was quite effective (and soulcrushingly boring) when nobody had any experience facing it, but once teams learned how to counter it, it largely fell to the wayside as a go-to style of play. If that's innovation, it isn't exactly the pinnacle of it. It was a fleeting gimmick that came and went in a single-digit number of years.
Beyond that, Pep is known for repeatedly botching it big-time in important games as his tactical decisions are routinely bizarre and ineffective. It's like he has this conceited need to tinker with formations and selections just to seem like he knows more than everyone else, and it tends to backfire, which is a large part of why he has failed so spectacularly in the CL since he left Barcelona.
While I wouldn't go so far as to call him a poor manager, he has only ever accomplished as much as you would expect anyone to accomplish with the strongest squad in the land; and quite often less, given that he has only ever won a European trophy when he had the strongest squad in the history of football at his disposal. And it's looking quite a lot like most of what he has accomplished was through cheating, so there's that. Financial and, possibly, literal doping is a shadow over his career.
He's a manager who has spent every day of his career working with the strongest squad of whatever league he was in, usually spending the most money, and with the easiest route to success. In light of that, I don't think he has done any more than the expected amount. His success in Spain can largely be attributed to Barcelona's golden generation, his success in Germany was automatic and hardly above and beyond, and his success in England has been in an era where absolutely all the other big teams were in a slump, a rebuilding phase, a recent revival, or some other period of less-than-stellar competitive capability.
In fact, it seems as if anytime another club has a really good season, City don't win. It's just that there has only been a couple of those. His teams aren't greater than the sum of their parts, he has just had the freedom to buy great parts, or inherited them in the first place. There's no doubt that he's a competent manager, but I've never seen anything more than that in him. If anything, he's just really good at landing the jobs that are most likely to offer the path of least resistance.