Well, the counterargument would be that we should always be looking to get better, and buying someone to relegate Kulu to the bench is what big clubs do.
Not saying it's realistic with the owners we have, but that may change and then that would maybe be more realistic.
As for Zaniolo, he has two exploded knees - a player with not one but two ACL injuries before hitting 25 is scary to me.
By buying Trossard are Arsenal looking to relegate Martinelli to the bench?