Hiya, you can enable/disable if adult rated stuff appears via the settings here: https://itch.io/user/settings
If games are still showing up despite that being toggled off then they're incorrectly tagged and should be reported so moderators can properly apply the tags.
I believe this is the default setting,too, and applies for anyone not logged in--so most explicit stuff has to be purposely toggled and searched for to display for anyone who might want to see it, rather than being thrown right into your face from the get go. The same way Steam handles it. Though admittedly Steam has more granular control over which tags you want to see/don't want to see--which could definitely help improve itch.io on that front.