This sounds good on paper until you realize that what is considered “social media” is up to whoever happens to hold that position. Even ignoring the fact that it’s unenforceable anyway, unless you require a real ID, wish is just straight up worse for all sorts of reasons.
The idea is nice, but actually putting it into law without opening the door to censorship and other side effects is just not plausible.
Edit: also, Everytime you read about a poll like this, ask yourself: what was the question they asked? Did it provide any context? Did it require any understanding of the actual underlying issues and laws? Or was it some variation of “think of the children”?
The politicians in charge of making the laws often lack the understanding needed to make privacy respecting laws. So it’s possible, it’s just not happening. They also listen to actual experts ready to little, but do listen to lobbyists.
This also doesn’t address the censorship side of the problems.
Just for a random example, literally the first thing I thought of: let’s say there’s a youth movement to affect climate change, or some other issue. They organize general protests, boycotts on “bad companies” and are starting to get somewhere (politically and affecting the bottom lines of these companies). This is coordinated using some online communication platform, think Reddit, lemmy or whatever (Facebook, whatever). Those that want it to “go away” can just include that in the list of sites that fall under thes “youth protection” laws.
Then there’s laws like that being extended it abused to do things that weren’t originally intended, which is also hard to safeguard against. Future legislation might extend the age range from 16 to 18, then to 21. With the list of blocked sites also growing conveniently alongside, and boom you got a nice censorship platform. Not saying that will happen, but making sure it can’t is what’s hard.