Segway
Their recruitment has been poor in recent years and that is the single biggest reason. You can have the greatest ideas in all the world but without the right execution it's all moot.
I'm actually quite worried about the game right now. Where is all the talent? City have always had an exceptional transfer strategy but players like Doku, Savinho and Nunes are all downgrades on their predecessors.
They're going to struggle massively to recreate the creative hub of De Bruyne, Gundogan and Silva. Who is the next big creative/attacking midfield talent? Musiala and then? Bellingham? Palmer? Who else is there?