Arsenal and Manchester City lose some games in last season, just that arsenal was not just lucky to get the title of the league and I'll agree with you that arsenal was not consistent in their games last season, even with the performance in their game it wasn't easy for Manchester City. Arsenal was really a threat to Manchester City last season, if Arsenal had pit more seriousness in their games getting the title of the league would have been easy for them . From what we saw in the performance of Arsenal's game in last season it is clear that winning the title is not a very difficult task for arsenal , they have the chance of grabbing it thus season if they can be very consistent in their games this season.
Arsenal have done their best but they still lose to Manchester City because in many ways Manchester City is superior to Arsenal, including the most influential thing is mentality, which is what Arsenal doesn't have.
However, if we look at Arsenal's overall performance, it is improving with each season, which means there is much better progress, so it is possible to continue and I am sure that if Arteta continues to build this team then soon they will be able to beat Manchester City and win the title. Premier League.