4) Lack of investment
In the modern game money talks. Leicester City have defied that concept this season but 9 out of 10 times its the big spenders that seem to achieve success. Manchester City and Chelsea have been prime examples of that concept.
Arsene Wenger does not have to spend the amount of money that his rivals do but that doesn’t imply completely ignoring the obvious areas of improvement in a squad. Their defense has been a problem Wenger has failed to fix for several seasons now.
Despite achieving a little more stability in the last two years Gabriel and Mertesacker have often been found wanting with Laurent Koscielny being the most consistent performer at the back.
Another area of improvement has been the striking department. Olivier Giroud and Theo Walcott are decent players but not the top quality striker that Arsenal have been screaming out for all season.
With players like Mesut Ozil and Alexis Sanchez in the team they lack a genuine goalscorer who can compliment the quality that their two-star players provide. Wenger had two opportunities to fix the issue, in the summer and this January but chose not to for reasons only known to him.