No, sorry. No.
Your legal name is important. If you ever get incarcerated, your legal name will be on the docket. If you have a license or passport, your legal name will be on it. Your taxes have your legal name, as well as any other government certificates you may ever have.
I virtually never write my entire name in forms. I bet I could use a pseudonym or fake name and nobody would care as long as the identity number is there. The only exception is passports where my legal name is important.
For any recreational/social purpose, what's the point of requiring legal name? How many "John Smith"s are there in the world?
But yeah, assigning GUIDs to everyone born in the world, like as "a93sz0sz" would allow uniqueness for thousands of years.
Guess what, my "street name" is used in "street" scenarios, my "immediate and extended family name" is used by my immediate and extended family (not my legal name btw, nor has it ever been).
What makes the legal name special in any regard? They are all used in their niche.
If you don't think that Facebook should require your official name, I get that. But trying to deny that people generally have one seems odd.