This is a stepping stone towards further control elsewhere, especially once a framework for enforcement is in place (which nobody actually thinks about when emotionally reacting to feel-good ideas like this). How easy would it be to expand ID based age enforcement to tracking ALL online activity and cracking down on "non-approved" speech? No thanks. I'll handle parenting myself.
Also, if you don't care about the age number, and think social media is just objectively bad...why are you on this social media site? Isn't posting here the definition of hypocrisy...given you're supporting what you believe to be worse than cigarettes?