The performance of Arsenal last season was above average because in all competitions they were outstanding in their performance but the problem that has been affecting the team from advancing further in the domestic league and champions League is the level of average players in the team. Arteta has been rebuilding the team in the last two seasons and they have improved in performance and their winning mentality has also increased but they need more experience to be able to withstand opponents in the champions league competition and this is necessary because last season they had the opportunity to win Bayern Munich to advance to the semi finals but they were defeated by Bayern Munich because of lack of experience.
Arsenal needs to bring in more players to be able to stand against Manchester City who stands as their biggest opponent in the domestic league so they need players with good skills and experience order wise they will keep playing well without winning trophies.