I like the way you are approaching this. I just point out clear inconsistencies in reasoning or faulry claims.I don't agree with the way I feel Gundogan is a bit of an easy target like you do, but it's maybe best to try and figure out why. I want to understand the 'haters' (if that's the term) more than I want to be scathing of them (I will admit I have been scathing myself occasionally).
So I'd guess it's that they believe the other players's sloppiness is a blip, whereas this Gundogan performance represents a continuing problem. If you read through a lot of the posts criticising him, there's a decent number of them with a real tinge of frustration going on.
Also, there's always some people that have just had a tough day and need to moan and for a moment to be understood. Easier to call out the player everyone's already calling out than someone who everyone is praising.
It's fine to conclude Gundogan was poor (he had lots of poor moments), but it's hypocritical to claim. Fern who was as poor ( worse in my opinion) was 'Great' ( as some have - coz he covered an Aubamayeng run once!) And in the same breathe argue how Gundogan was poor.
The other argument is to claim Gundogan 'caused' or was 'the reason' for Fern's poor play.
The surest red flag that some player is a scapegoat is when you see him being blamed for someone else playing poorly.
That is Ipso facto Scapegoating... And there is enough of that being served at Gundog's restaurant :)