People monetize children's videos by saying they are not for children. Google have been in hot water for serving ads to children and the way around it is to remove ads (or classes of ads) from childrens videos.
Creators wants that extra money so they try to post children videos and calls them “for adult”.
Obviously a mistake was made. But let’s be real: it was made in an attempt to right wrongs, not in an attempt to wrong rights.
Kids are the ones to whom videos need to be restricted.
Adults should be able to watch both kids and non kids videos.
So the only thing needed is for creators to mark a video as “for kids” and the algorithm to confirm that it actually is for kids.
Nothing else should even be available for kids.
If they want, they can have an additional option for creators which is “definitely not for kids”, much like you’d have an “explicit” option for music.
These wouldn’t require an algorithmic check and simply not be available to those under 18.
These videos will make less money (at least, I've been repeated told less tracking is less ad money), so Google has to worry about people mislabeling their content to get better ROI.