Nicolas Jackson also play in Premier League while Osimhen plays against the likes of Salernitana, Monza, Lecce and Empoli. This is a major context, one of huge importance because we've seen fairly mediocre strikers score a ton of goals in Serie A.
Belotti with his 26 goals for Torino, a 36 year old Giroud scoring the same amount of goals as Osimhen in not so much more minutes, Higuain scored 36 goals in 15/16, Dzeko (I don't think he is mediocre, he is pretty good) 29 goals in 16/17, Icardi and Immobile with 29 goals each in 17/18, Quagliarella with 26 goals and Zapata with 23 in 18/19, Immobile with 36 goals in 19/20 and the list goes on.
These strikers scored more than Osimhen, but none have been talked about as elite strikers. The reason is because at that time there were actual elite strikers around and so we didn't have to pretend that decent strikers are world class.
As for your comment on Osimhen being easy to create chances for, it is the exact opposite. It is easy to create chances for Nicolas Jackson, while Osimhen is only a poacher and so you need perfect delivery for him to be able to do something. He is more invisible than Haaland a lot of games, and we all know how Haaland can look like if he doesn't get service. Even Spalletti (who he won Serie A with) said he needs to do much better in terms of build up, link up and working together with his team mates.
Osimhen is far from a goal a game striker, and even if he was, he has only shown it in Serie A where Immobile and Lukaku shine. He doesn't perform in CL so there's that too.