David is a massive loss. Just bloody massive.
Kevin is as part of the problem as anyone though. Gundogan is playing well so it must be Rodri, Torres, Foden, Sterling, Mahrez and Bernardo you are classing as 'mish mash of average/absolute turd around him now'.
Kevin is a senior player, as often as not Captain, he isn't paid his hansom salary + bonus to be frustrated. He is paid to contribute and provide leadership to the team. His current contribution falls way short of what he is capable of. Hence the criticism.