In a comparison between Lukaku and Osimhen, I would definitely put Osimhen ahead considering recent performances. However, Osimhen's wages are higher than Lukaku's. However, we have seen better performances from Osimhen in the last two seasons. But Lukaku hasn't done so well in the last few seasons.
But since Conte likes Lukaku, keeping Lukaku in the squad is probably a good decision for the Napoli management. However, if Osimhen and Lukaku were at the same time in Napoli's attack, Napoli would have been stronger. But Conte is not interested in Osimhen. However, expect to see a better performance from Lukaku. But it is not certain whether he will succeed.
I think everyone thinks the same as you even though Lukaku was a talented striker in the past but if we compare his abilities Victor Oshimen is actually better if seen from all sides if Antonio Conte uses these 2 players in the front line, Napoli will most likely be stronger in attack and their chances of competing in the Serie A title hunt will be greater but using these two players at the same time is not good for Napoli's finances because Oshimen has a high salary so Antonio Conte had to choose one and he chose Lukaku who felt more suited to the coach's tactics, but I don't really expect much from Napoli's performance this season even though Antonio Conte is the best coach in Serie A but Napoli is not a club that can be built easily.