Mikel Arteta has done a fantastic job this season. This is really commendable, if they can maintain the consistency at the end of the season, maybe Arsenal would be the champions of this season. But it was their misfortune that they could not win the championship. As Arsenal will play in the Champions League next season. So they need a stronger squad. The Champions League and Premier League are very competitive. It is much more difficult to maintain consistency in both places. And so in addition to strengthening Arsenal's squad, they must also keep their bench team strong. Otherwise, Arsenal's performance will suffer badly if a key player gets injured.
Arteta doesn't have good backup players when the squad feels tired or injured, of course Arteta doesn't have other players to rely on, even though Arsenal could have won the league this season, unfortunately Arteta didn't really manage their players at the end of the season, Arsenal have been around for so long top of the table before but unfortunately at the end of the season they looked tired and inconsistent.
Manchester city took advantage of that and shifted Arsenal at the end of the season by consistently getting successive wins to reach the treble winner goal, but apart from that Arteta has been working well it's just that there is a lot that needs to be fixed so that next season they can compete again to win the league, especially recruiting many new players for arsenal.