I have fixed this - all clubs from the clubs/list endpoint should now be correct again.

Thank you for pointing this out! This is due to a discrepancy in the data where some club names have changed. I will look to make all club names consistent in the future. The endpoint to find players of Napoli is ‘Parthenope’.
In the meantime, you can always look up a player’s “club” property to find what the endpoint should look. For example, you could look up Victor Osimhen and find that his club is listed as “Parthenope”.