Prohibition is effective, it's just that it doesn't work for easy to manufacture compounds such as alcohol or marijuana. Every known human culture has independently discovered alcohol, and marijuana is a weed that is ready to smoke in its natural form.

As far as social media goes, my country has reached a point where TikTok and Facebook are preinstalled on every phone. If a parent buys their kid a phone and removes them, they will reinstall themselves after an automatic update. When you take into consideration the "streamlined" registration process, one can argue this is a means to target prepubescent children.

...I guess an 8 year old could download a VPN and steal their parents identification, but I feel like some form of prohibition would help.