Arteta needs to ask the club owners to spend money on a quality striker who can consistently score goals throughout the season. Benjamin Sesko, Gyokeres, or Osimhen are a few names worth recruiting, regardless, Arteta must fight to secure one of these three forwards. It makes sense if their transfer fees are high, they possess the quality needed, and that would increase Arsenal chances of winning trophies next season. If Arsenal fails to bring in a good striker, let alone challenge for trophies next season, they might even struggle to compete in the top four. We know Man City will bounce back after their squad overhaul, Chelsea will be stronger than ever, and Liverpool are still in top form. Arteta certainly understands how big a challenge he will face next season.
When it comes to Arsenal getting a quality striker it looks like is a joke because the board members are not showing any signs of listening to the manager Arteta and sometimes too it like the manager is satisfied with the set of players that are with him even if there are some who doesn't show that sign of seriousness in them. But this very issue need to be cover before the end of this transfer window, the players you mentioned are all good strikers but nothing is being done to get them especially the Sporting player Gyokeres who have made it clear that is Arsenal over every other club and if you talk about Osimhen I don't think the Gunners are willing to go for him but they need his kind to make them challenge for titles and not second position every season, wish it was a trophy to give to the Gunners.
For the teams you said are getting themselves ready for next campaign, I'd say is only Manchester City and Liverpool who are ready to fight for the title next season, Chelsea are still in the market and in a confused state, a number 9 has been brought into the team but something special is missing in that team and that's a right winger, the Blues will struggle in the wings especially if is only one side that's operating properly but for now if we are looking at the seriousness in teams that are in the market we shouldn't mention Arsenal because they are also confused and is like they are finding it hard to figure out their problem.