Bournemouth conceded two goals a game when he started last season and he managed zero goals and two assists (I think they were both in the 6-3 against us) personally all season. As soon as he was dropped for the last five matches, they went unbeaten and took 11 points from those matches to stay up.
This season he's made 11 league starts for Arsenal and they've won 3. 1 goal and 2 assists all season.
So in two seasons he has managed one goal and four assists, he offers no cover defensively and despite looking flashy on the ball, doesn't produce anything going forward.
Above all that though, he's a prized bellend.