I agree with you and I also see that the weakness lies in the mentality. Almost all of Arsenal's players have great abilities, but they lack the mentality that has led to their failure to win the Premier League title in the previous three seasons.
Arteta needs to improve the players' mentality when facing competition, as they have so far lacked confidence.
Finishing second in the standings for three seasons isn't bad considering the quality of the players Arsenal have, so they need to develop a winning mentality for next season.
In this context, of course, it is not only the players but also the coach because after all, when talking about Arsenal, the situation must be put together where not only the players are guilty here but also the coach who is unable to maintain the rhythm even though their chances are very good.
In the last few seasons it has always been a matter of mentality and performance that rises and falls quickly to become a problem for Arsenal which makes the opportunity that has actually been very wide open just has to be lost.
The same mistakes are always made but they cannot fix this so in the end their achievements only remain running in place because only runners up can they get even though the opportunity is always there.
This season, they have started with the hunt for new players but when the same problem returns then whoever the player is then the result is the same because what currently needs to be improved is the winning mentality that must be fertilized and until now Arteta has not been able to do this.