I was questioning the same after this debacle. I felt the same about Hart during the 11/12 season but there is no doubt he dropped off after that. I used to be took back by how well he could pick out an accurate long-range pass up-field, then when Pellers came in he started kicking it out of touch every time and certainly no where near no.2 in world football.
Even back in 11/12 or 12/13 when Joe was on world class form rags were exclaiming DeGea was no.2 in the world and still fervently do, even many other football fans and some City fans too. DeGea when he first came, flapped at absolutely everything in-front of him and was terrible. He's obviously come on a lot after taking time to settle in over there but still, he's not as good as Courtois was at Atletico. I don't see the ability one on one ability in DeGea that is probably Joe's greatest strength (has always continently pulled us out the shit over his City career), obviously a big strength of Neuer too. He can be a great shot stopper reaching for shots going into the corner etc. but not any more so than Hart. In recent years Hart has been weak getting caught out with low shots to the corner though. I think he's just not kept up to the high standards he set himself a few years ago.