They absolutely work. I'm a parent, my kid plays games. I have yet to have any concerning close calls with NSFW content. People who make adult games (by and large) don't want kids to play their games.

If the platform doesn't want kids to see them, and the creators don't want kids to see them, it's pretty easy for kids to not see them.

If creators, platforms, and users all say, I would prefer to not see the content, it's pretty easy to make that happen.