He's a good man manager and a fairly alright tactician, it's the boldness and sheer decisiveness of Pep that he lacks (not that he should be held to that high of a standard). Pep knew exactly what he wanted, went right down to every detail in a meticulous system, and was clear in implementing it. Combine that with the fact that he was a true innovator and intellectually brilliant, and you can see why he's one of a kind. He's the most proactive coach I've ever seen, always a step ahead of everyone else and really defining the team around him. 99% of other coaches are reactive, meaning they handle things as they come and are there to facilitate, not create. To put it into a metaphor: if other managers are there to improve and tweak the machine and oil it so that it runs smoothly, Pep is there to take apart the machine and then build an entirely new one from his vision.
Tata has done brilliantly with individuals which is why our players find form so easily. He's also good with a general formation sense of tactics which is why we've been versatile in our play. Because of this, he's done pretty well so far with the team considering how much worse Tito was and how tough the league has been this season. However, if you want a romanticized Barca team (which is also the most successful kind) then you need a coach with a really strong direction and the desire to implement it.
I wouldn't mind having Tata for the next few seasons as he's obviously not meant to be a long term successor or anything. After that, I'm not sure who there is to aspire to Pep's level of managerial brilliance even if not mirror it. A huge part of me wishes that he'd come back after the Bayern project, though there's nothing pulling him in that direction now or anytime soon. Other people who share the same qualities and philosophy even if not to the same magnitude would probably be someone like De Boer, Laudrup, Oscar Garcia, and maybe Luis Enrique?
We'll see soon though. Bright, young managerial prospects are coming around often and it's only a matter of time before one presents himself as capable of being what we need in a long term manager.