Arsenal were actually better last season than they are this season. They lost so much form this season and I believe it's due to fatigue. A top club needs squad depth to remain at the top and a very good rotation. Last season, Arsenal were still in form at this point of the season. They got bad after a couple of injuries and fatigue.
Fatigue is a very big problem that prevents high-flying teams. This usually affects teams that press very much in matches. It affected Liverpool too after they won the EPL.
Arsenal will make the top 4 but they won't be among title contenders.
How are you sure Arsenal will finish fourth in the league table with the way they are playing now? I don't think so. Tottenham, on the other hand, will finish fourth because they are performing well without their key players. When they play against Manchester United, they perform well, and I am confident that if their players return before they play against Manchester unted, they will defeat Manchester unted in the match.
Every time Arsenal starts a new season, you will see their performance and think they will win the trophy because they played well last season and then fucked up and let Manchester city win the title, this time again everyone believes Arteta will not make mistakes this season and will win the trophy but they fail to win this time because i don't think they can win this season because Manchester City and Liverpool are now in contention for the title. I believe Arteta will quit Arsenal if he does not win a trophy this season, as I have heard rumors that Arteta will be the manager of Barcelona next season if Xavi leaves Barcelona.