No it isn't; children have always been able to borrow the same books from libraries as adults, read the same newspapers. Just now much of the information doesn't live in books or newspapers.
Banning children from social media is like banning children from movie theatres. A ban should consider that (1) different restrictions are appropriate for different ages of children (e.g. 12 vs 15), (2) depending on the country (e.g. the US with the First Amendment to the Constitution), children may have information access rights that parents can take away but governments can't, and (3) children in unhealthy relationships with parents or guardians (e.g. transphobic/homophobic parents of LGBTQ+ kids) should be able to access some kinds of social media without letting their parents/guardians know.