I think Doug gets more undue criticism than most coaches for a couple of reasons:
He was without a doubt the least exciting coaching hire - no head coaching experience, didn't call all the plays at KC, very little coaching experience altogether etc. - and no other team expressed an iota of interest in hiring him.
There's a perception that Dough Pederson is Andy Reid-lite i.e. all the things people hated about Andy they are automatically assigning to Doug.
His demeanor and the way he speaks is a little off putting for some. He doesn't come off particularly confident or charismatic and sometimes he can appear a little aloof.
So you take all these criticisms that aren't really justified and aren't at all Doug's fault and many people already have this altered/skewed perceptions of Doug.
So when Pederson does make a very questionable decision like giving Blount 0 carries in Week 2 or going for it on 4th and 8 at midfield - people are automatically going back to their presuppositions about Doug - he's unqualified, he's crappy Andy Reid, he's an idiot etc. If this was Jim Schwartz going for it on 4th and 8 I highly doubt he'd warrant the same criticism that Doug is getting.
Now I want to be clear - I'm not the biggest Doug Pederson fan. I think his play-calling is questionable, his challenges have been abysmal and his seeming over reliance on analytics shows a coach that lacks the confidence to go with his gut/feel for the game.
However, Doug Pederson has this team competing week in and week out. He makes adjustments between games and at the half that almost always have a positive impact and he's not above changing his strategy in the face of failure (a la Chip Kelly). That's more than you can say for a lot of coaches in this league.
All that being said there are 13 more games (at least) to play this season and we're going to continue to learn a lot more about this head coach over their games. I'm reserving my judgment on Doug until he's had two full seasons under his belt to make a proper evaluation.
Is he underrated? He's definitely underrated by the people who are ready to fire him 3 games into a 2-1 season. But at this point he hasn't shown me enough to believe that he is a true difference maker or game changer at head coach for this team. Time will tell.