See I think Lucas has been playing okay this season, just that having a RW who doesn't occupy any attention from the defensive line makes it easy for teams to hold shape and mark Kane and Son. Lucas only takes the ball from a man beside him in midfield and carries it, rarely makes clever movement ahead of the ball. For such a talented player it's remarkable how little he's added to his base skill level.
Don't know about Lo Celso RW. He could be good there but he needs bodies around him and we don't appear to be coaching much attack. Lucas is a kind of Traore-lite in that he creates unstructured attacks by himself.