itch.io terms forbid anyone under 13 from using the site (because of COPA US law), but it looks like these things can apply to up to 16 years of age. Thanks for notifying me, I'll take a closer look at this stuff. Having a regular age gate on top of adult content is definitely something we need to add though, regardless of these changes.
That being said, if your game has any sort of information collection at all, then you must provide a consent form. As it stands now, itch.io will not ask for consent on behalf of individual creators. (Thought we may set up something to stream line this in the future).
Generally, this means that if you have any kind of sign in or analytics collection that includes personally identifiable information in your game (like username, email, ip address), then you must show your own dialog within the game.