Granted this law was more clear cut with 14, 16, and 18 being the dividing lines, but it definitely fails to concisely define social media.
The other issue is how do you verify age, and that has been another difficult question if you think people should have reasonable expectations of privacy and aren’t comfortable with the “enter your birthyear” forms.
The main difficulty is defining social media in a way that doesnt restrict other modern communication, education, idea publication, operating a business, shopping, sharing ideas, etc.
Should such laws block Etsy, your family’s Nextcloud, a school ran web forum that only students/parents/faculty can access, Crash Course on YouTube, encrypted communication between your family, etc?
The other difficulty is defining the term “children” consistently. Many US states have simple categories that go all the way to 18, if not later.
Should there be a difference in laws for access for toddlers, elementary ages, and adolescents?
If you think these are easy questions, I suggest you look at the dialog around the UK’s Online Safety Act where they are having to answer these questions after the fact.
If you keep forgetting them for another ~15-25 more years they might have value in the retro space.