I dunno, mate. Moaning and groaning has always been part of being a football supporter. Or maybe that is just because I am a City fan. I used to regularly go to games when we were somewhere North of Oblivion, and we moaned about the chairman, the manager, the players, etc. But we did have our inflatables!
The thing with United is that expectations are incredibly high, especially as the club are always topping the Forbes rich list. This makes many fans feel that the cream of world footballing talent should be going to United, rather than elsewhere. It is understandable in that context.
Being a supporter inevitably involves criticism: 'why didn't we sign player X' etc.
Didn't the whole Green & Gold thing amongst your match-going support indicate a bit of 'doom and gloom'?