In one on one defending, Coleman is one of the very best. I have never got the "he cant defend" nonsense. He might get caught out at the back post occassionally, but so do most full backs at times. Troy Deeney and other big CF's like to drift towards Coleman/RB so that they can be hit with diagonal balls and to stretch the centre halfs. This rarely happens on the other side as right footed fowards naturally don't like to be out wide right.
Getting forward he is also one of the very best... when he is not hindered by Walcott hiding on the touchline and/or having zero intelligence to drift in to create space or to spot Coleman's runs. Not surprise Coleman has looked back to his normal best with Richarlison who helps out defensively and also has a brain bigger than a pea.
Carrying terrible players has a bigger impact on some players than others, Coleman being one of them that is adversely affected. Gueye could carry awful midfield partners, he is one of the few who could. Baines used to carry our series of awful left wingers... Cleverley, Kone, Mirallas,DCL and whatever other awful footballer than was shoehorned into that position over the years. Thankfully we have 3 players competing for that position now.