Having 2-3 good players in a particular position is always beneficial to the team because it motivates everyone to play at their best. For example, Manchester City has several world-class players sharing the same wing, but only the ones who are at their best start games. R. Steeling and Mahrez occasionally sit on the bench to allow Foden and B. Silva to play. Saka is a versatile player who can play LB, RW, LW, and Number 8 at times, so I don't understand why any potential player shouldn't be on the squad. On the Chelsea team, Zirech, Pulisic, and Odol all play the same position. More depth in the team, the better.
I agree, I just feel that Arsenal is not on that level where they can do that just yet. Example - Saka is often playing on the left because he's basically the only one in the team that can play there. He started as a right-sided midfielder and he was playing better there, so why not sign a left mid and put Saka back on the right side?
If they buy Kulusevski, he plays exclusively on the right - meaning Saka has to keep playing on the left. And what happens with Martinelli then?
All that would be good competition if Arsenal had a great all-around team. But they still need a CB and a CM more urgently than they need competition on the right wing.