Most of your post has merit. He is not the finished article.
He has struggled in some games and he probably would have played much less minutes if the squad was not so depleted.
But to put the failings of the team this season on him, and to write him off is not right.
The injuries throughout the squad, the levels of fitness, players having to play while injured, Our leaders, De bruyne, Dias, Walker, Rodri, Foden, for one reason or another not being able to contribute regularly or at the level desired , and most importantly confidence levels are the major reasons we are struggling.
Lewis has many attributes, some you acknowledged, not the least that he is one who continues to look like he is playing to a maximum effort, whatever his performance, for whatever reason other players do not. He may not be the player to turn our fortunes around single handed, but he is far from the cause of them.
My main point to you was that you write players off very quickly, only to be proved wrong,our 4 in a row are an indication of that.
Professional footballers who Play for Pep do not get to do so by chance.
I believe a couple of signings, fitness, and the option of rotation will soon bring about a change in fortune, and Lewis will be an important part of that,pp as Rodri and others have been in the recent past.