In fact, Arsenal also joined the hunt for Osimhen in the last summer transfer market, but an agreement failed to materialize because Napoli asking price was considered too expensive, Arsenal was reluctant to pay Osimhen release clause which reached 100 million pounds. Arsenal are a good choice for Osimhen, he will develop into a fearsome striker under Arteta. Maybe they will try to negotiate again with Napoli in the January transfer window to add strength to the front line after not bringing in a single striker in the summer transfer window this year, his arrival could also help Arsenal go further in the UCL. However, Arsenal are not the only EPL club that wants to bring in the Nigerian player, Chelsea are also very interested in bringing him in.
Two biggest barriers for Arsenal in a transfer: Request of expensive transfer cost from Napoli as that club never want to sell their players at cheap costs. Request of Osimhen with a lucrative salary as the player will not be ready to receive not too good salary offer from Arsenal.
It's impossible for Arsenal to break their player salary ceiling just to satisfy Osimhen and get this player in a paid or free transfer. Years ago, they refused to satisfy their captain Aubameyang who was important striker in their squad. That contract and salary conflict forced Aubameyang to leave Arsenal and it's not too far. Arsenal are ambitiously in building up a more competitive squad, especially in their attacking with a focus on striker position, but I believe they will not do this with all possible costs.
Breaking a player salary ceiling is always bad in long term and I doubt that Arsenal are ready to make this club policy break.