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.
Arsenal's near success syndrome have limited them from claiming the English Premier League title in recent years especially in the last two seasons that they dominated the top spot more than any other team managed but still ended up not winning the league. This season that Liverpool have dominated more, I don't think Mikel Arteta's Arsenal will be able to finally lay their hands on the league trophy.
I think the major problem that's haunted and limited Arsenal chances of winning the league in the last two seasons is the mentality of the players. The club players in my opinion lacks the strong mentality of a team that believes so much on themselves and until they work on their mentality, I don't think they'll be able to lift the league trophy