He already did this when he went to the Treble winners in 2013.
How is joining PSG any different?
It's very obviously different as there were teams in Germany that it seemed could match Bayern in a given season. He did a great job to ensure that was not the case. It was his first excursion away from Barcelona. It's also not a case of going to manage another team with unlimited money, even though Bayern were more rich than the competition. He earned that right to take a job like that. However, it is no longer the case in France that a team will approach PSG. Of course, everyone has to get a paycheck, etc. But running away from Barcelona was rather strange to begin with, and to manage PSG would be stranger.
I really don't think that's going to happen though. It doesn't make sense for him to leave for a host of reasons., even though it's possible he would.
While you inaccurately stated that he would get the deserved criticism if he went to PSG. First he is not above being criticized I have critiqued him while at barca and at city when his mistakes were obvious. No one is perfect after all. Pep's biggest criticism is that he coaches super teams. As if Barca wasn't 4th and a mess when he took them over. As if City ever reached the heights they did without Pep. So going to PSG wouldn't prove the haters right he is what he is whether he goes there or not. I personally wouldn't understand the move but lets say he does go there and wins a CL. What then?
But City won two leagues without Pep, won a double without him, etc. City hit heights without Pep. They were only the second team in England to score more than 100 goals in a league season. Their European results, on the other hand, were just acceptable. Their results were something to be proud of though, we're not talking about a team that didn't win anything before Pep got there.
Also, I don't think it's true right now that he only coaches super teams with unlimited bank accounts in comparison to their competition. If he goes to PSG, then yes, that would be largely true on the balance of things. That would make three teams that were by far the richest in their league, that spent the most money on their squad prior to his arrival. The criticisms that some people have about him attempting to avoid pressure over the course of a league season would be validated to some extent. I will reiterate I do not think he'll do that.