For the saves he makes he's been good. I'm not doubting his shot stopping ability in the slightest, however, how many of those saves would he not have to make had he been more aggressive or been better at directing his defense? And despite what you may think, his positioning is not good, does not anticipate well and his handling is horrible. Not sure what you're even talking about there. In fact, if we compare De Gea's stats to Allison
-------------------Punches---High Claims---Sweeper--Saves
De Gea-----------5------------------8-------------------5-----------111
Allison-----------18----------------17-----------------23----------62
So in a team that has a far superior goals against than we do, Allison is 3 times more active in helping out his defense than De Gea is. So think about it....if those 111 saves that De Gea made, how many would he not have had to make if he was more active? Or on the other side of the coin, if Allison wasn't as active to help his defense, perhaps the opponent would have more shots on goal which would allow Allison to make more highlight reel saves. Sure, he would likely concede more as well, but they wouldn't be considered his fault, just like De Gea isn't blamed. In fact, he will probably be rewarded for it...
David de Gea Statistics | Premier League
Alisson Statistics | Premier League