Hello! @rcccompetente
Welcome to the LastPass Community.
Once you share a password and you choose to don't allow the user to see the password, while the user open the items details using LastPass, the Password won't be display, to use the shared password, the user needs to have the LastPass browser extension due to the autofill is done using the browser extension.
There is a limitation about this tool, if the website allows the user to see the password unfortunately, we cannot control the website settings.
Please let me know if you need additional help.
Greetings!
Verlaine | Customer Care