Speaking of Arteta, it seems that you are wrong, so far the players who have been bought by Arteta in the last two seasons have certainly contributed quite a lot and so far in my opinion no one has failed except maybe Gabriel Jesus who is a little beyond the expectations they wanted and of course injuries have made Jesus unable to be at his best so far, If you say Ramsdale and Havertz are failed purchases of course you are wrong, since Ramsdale came to Arsenal, Ramsdale was immediately able to get the position of Arsenal main goalkeeper at that time to replace Leno and indeed the competition with Raya made him start to become a second goalkeeper but that does not mean he is a bad goalkeeper, while Havertz at the beginning of his arrival was of course quite disappointing but slowly he was able to become a mainstay of Arsenal and scored 13 goals and 7 assists, Did he fail?
It's evident that Arteta's signings have made good contributions to the team's squad over the past two seasons. While some players have not met initial expectations, they've still brought value to the team. Gabriel Jesus have not really performed as expected due to injuries and perhaps being slightly beyond anticipated performance levels, he still has the potential and has likely added competition within the squad.
Ramsdale joining the team made him take over as Arsenal's main goalkeeper, leaving aside Leno from the starting lineup. Though he faced competition a little from Raya, it doesn't cover his abilities. It rather shows the competition Arteta has created within the team. Also, Havertz's journey at Arsenal started with some disappointments, but he's proved his worth with 13 goals and 7 assists. This underscores Arteta's skill for nurturing talent and allowing players to adapt and flourish within his space.
While there may be various success ranges among the players, it's wrong to label them failures. Each player has been impactful to the squad in their own way. Arteta's ability to work on his players to blend to his vision for the team speaks of his managerial abilities and portrays that even players who initially derail can find their bearings and become essential to the club's success.