Mentality has always been their main problem in the last 3 seasons and even with the amount of money that Arteta has spent on players to improve the quality of the team, it seems that the mentality problem has not been resolved.
A team like Arsenal who has spent a lot of money in the last few seasons needs trophies not just improving the quality every season and it seems that Arteta can be considered a failure now, regardless of what he will do but if he can't improve the team's mentality and maintain the team's consistency until the end of the season I think the result will be the same as the last 3 seasons.
Overall the squad that Arsenal has is quite good in all lines, so I don't think there is anything wrong with the players that Arsenal currently have.
This season will be tested again how Arteta can achieve better results or not because three seasons are in the runner-up position not something that can be proud of because successively always fails. Arteta has a number of good players in the team but when viewed in terms of experience and mentality of this team does not show something effective after the current season and eventually fail to maintain existence and submit the title entirely to other teams.
There are a number of things that need to be improved by Arteta next season and the most needed in my opinion brings pure strikers to support a more productive front line. The last to strengthen the defense so that Arsenal next season can be much better than the previous three seasons.