Osimhen is a young player and he can't be counted as a stable player, he just had one good season with Bapoli and we can't make sure if he will have a good performance in other teams like Chelsea or other teams, on the other hand, Napoli asked him for a huge amount of money and paying this money for Osimhen can be a risk for any team.
however, he did not play alone. he can play very productively at a young age, of course not because of the skills he has but many factors such as the trust and strategy of the coach and also the support of the squad which can indeed make him a young monster on the front lines.
if he gets a new team with a formation or a team that doesn't support him as well as he did when he was playing at Napoli. of course that would make him a failure in the new team.
but he is still very young, if he is held by the right coach and also with the right club maybe his greater potential can be seen.