Well, it is not irrelevant, if you are first team you will play more games. The quality bit is very subjective, it doesnt matter what you, me or anyone else thinks as long as the manager thinks they are good enough.
Again, I have never mentioned that he is not backed, he has not been backed enough to close the gap.
You are wrong here in my opinion. I agree you have to make do in some instances you have to make do. Let me ask you, If one of Martial / Greenwood/ Rashford are injured and the other has played alot of games, who do you bring in?
Arsenal - Auba, Lacca, Pepe, Saka, Willian, Willock, Martinello
Chelsea - Werner, Havertz, Giroud, Tammy, Mount, Pulisic, Ziyech
City - Aguero, Jesus, Sterling, Mahrez, Ferran, Bernado, Foden
SPurs - Kane, Vinicius, Bale, Son, Moura, Bergjwin
Manutd - Martial, Rashford, Greenwood, James, Ighalo, Lingard
James, Ighalo and Lingard wouldnt even get into any other squad, let alone come as first rotation option.
You expect our manager to out perform other teams who have better quality in the attacking half?