Please read the answers in this thread.
OP had that setting active and forgot that it was active.
If the setting is not active in your account and you see nsfw games that will have one of those reasons:
You are browsing an adult tag and confirmed that your are 18+. There is a box now that asks for confirmation. An example for an adult tag is "adult".
The games you see are not properly marked as nsfw or you only think they are nsfw, but are not.
You do have the setting for adult content active, but think it is turned off. It is on the first page you see when going to settings and reads
Content — How content on itch.io is shown to you
- Show content marked as adult in search & browse
I have that setting off and just visited https://itch.io/games and https://itch.io/games/newest and scrolled some ten pages.
There were the occassional games about dating or romance, but no obvious nsfw content.