Don't you have to log in to get that content to show up by default?

Yeah and? 12-year olds have reddit accounts for things like gaming or other discussions. I think if you go to r/All it features nsfw content

It's still off by default, especially on mobile.

And if you have a kid with unmonitored access to the internet, they're going to access nsfw content regardless of what a site operator does.

I think you may still have to flip a switch in settings saying you're OK with seeing that–but really you don't have to go very far to find content like that anyways, just click on the comments for any post and you'll find something questionable quite quickly.