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.
Arsenal 3 consecutive seasons to win 2nd place is certainly a good achievement because it indicates that Arsenal is a strong team but it's just that what is more desirable is to win 1st place at the end of the season, and indeed until now Arsenal have not been able to improve that, now I can only hope that Arsenal can be better in the coming season. actually about the reason why Arsenal always can't win 1st place, of course, it's quite simple. yes, in my opinion, it is also a result in terms of mentality, of course, Arteta still needs to improve because indeed with a strong mentality, of course, it will have the potential to make a player more enthusiastic and of course it will potentially be able to achieve what he aspires to.
but in my opinion one of the reasons why Arsenal are always difficult to become champions is of course because there is one of the players like there is an injury while there are no reliable players to replace the position of the mainstay players, for example like last season where Bukayo saka was injured, try if you have a strong backup player then surely Arsenal will potentially always consistently win when competing and finally will be able to also become champions.