Arsenal failing to win the league is as common as it gets, been true for three decades, whenever they looked good they ended up playing against some team that is better and end up failing. The most common issue they have is that they end up losing near the end, their momentum doesn't carry over to last third of the season and because of that they end up losing and that's the most important part.
As long as Arsenal could just play the whole season at the same level, I am pretty sure they could have won at least one title, but they always start great and then get worse gradually. If they had good subs and a big depth then they would have been better, it's clear that they faced so many injuries, and because of that I believe we should not judge them, injuries do make a team weaker, but if they had a proper depth then they wouldn't have this, they could have done better without a doubt. Unfortunately they are not looking that great at the moment.
Last season Arsenal was just one step away from winning the trophy, unfortunately in several matches they lost points which made City eventually win by 2 points and retain their title. This season Arsenal's performance has been a little inconsistent and several factors have caused them to fail to win several matches, for example several players were given red cards, besides several core players were injured. Plus, Arteta had time to change his system and strategy. Actually Arsenal is quite competitive with his players, but there are things that Arteta needs to fix such as dependence on one player. For example when Odegaard was injured, they lost a creative midfielder in terms of building attacks. In addition, Arteta should have had one pure striker that they can rely on to be their goal-scoring machine. Well, sometimes Arsenal have difficulty breaking through opposing teams that use a defensive system. But if they have players who are indeed specialists in scoring goals, of course it will be very useful and increase the sharpness of their attack line. Unfortunately Arteta did not bring in the striker who they actually needed. By the way, this season there are still enough matches, Arsenal still have a chance even though it is not easy to compete closely with Liverpool.