Arsenal has indeed continuously improved their squad depth. While they have consistently failed in several seasons, consistently finishing in second place, the team has never given up and continues to strengthen their squad, which was already strong last season. However, the team has been unlucky, and their players' mentality has sometimes weakened during matches.
Performance improvements will be meaningless if Arsenal lacks the right strategy to win titles, and those improvements will be futile.
Arsenal is overly praised, and rightly so, as they consistently bring in high quality players, but consistently fail to win titles.
Meanwhile, Chelsea and Leicester, who are often underestimated, have both won titles in the past decade.
In my opinion, as long as Mikel Arteta remains at Arsenal with the same strategy, I will always doubt Arsenal, and there will be no improvement for me.
This is an important point you have made, I also agree with you that Mikel Arteta needs to apply winning strategies this season to get a breakthrough through. Arsenal play good football but when it comes to winning games that matters most they lack that winning strategy to pull through, this has always been the problem and it needs to be fixed this season else Arsenal will only come close again and fumble.