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.
You dont know what you are saying mate. Arsenal cannot win any title if they are still missing the little details. Depth, striker and team force. All the players you see there wants to win a trophy, if they lack the winning mentality they wont emerge to the semi finals in the Champions league, and also wont finish second place in the EPL.
Their problem has always been for the board to get them more player to reduce fatigue and injuries. In a long time, this is the best summer for most Arsenal fans because the owners have actually pay attention to the details.