Maguire and Lindelof are both comfortable playing the ball around the 18 yard box which means we can hopefully pass the ball up the field and use our quick mobile forwards.
Smalling couldn't pass to the right standard which meant a hoof upfield to Lukaku/Fellani - the centre backs impact on how you want to play.
A decent defensive midfielder would make both look very different Matic never seems to take responsibility for long balls leaving one or the other to come forward and creating a dog leg.
Shaw can't seem to mark or be in the right place which again pulls Maguire and Lindelof apart. First Arsenal goal Lindelof stops the near post threat and if Shaw does his job he blocks or clears which Young would do.. Second goal Rashford causes the problem by not challenging Lacazette.
Maguire has a decent range of passing but the lack of midfield options means he is often having to pass longer. Arsenal we hit loads of aimless long passes up to Martial/Rashford not down the channels but to hold up.
Not many teams play 2 centre forwards and not 2 lumps so we only need one big powerful centre half the second needs to be a clever ball player who is an excellent positional player - is it Lindelof? Don't know but these 2 aren't the major problem.
A dominant defensive midfield player and an excellent passer further forward should be the 2 priorities. A clearer upper and a creator. We are wasting the pace we have.
oh and get rid of Shaw he can't seem to attack or defend beyond the average.