Alternative Social Media in Europe

This idea might be quiet stupid and unrealistic, but here me out.

What if, we as an online community/social media community developed our own Social Media App. A little like what AO3 is for fanfiction. So it would be non-profit, meaning there wouldn't be yet another billionaire with way too much power. It wouldn't be chinese, so no one could sell our data and no one could censur our content (especially political content). Soo many people on AO3, minecraft and the internet in generell do so much stuff voluntarily, woudn't it be possible for us to make this work? I am so pissed that whenever I want to use a Social Media platform a automatically support some billionaire I really don't agree with and I can't be the only one.

I have no clue about any of this (obviously), but please tell me everything that's wrong with that idea, what we need to think of, how we could pull this off...

Bonus if it's european, cause I don't really trust the US atm

Don't just tell me it's not possible, tell me why it's not possible and let's collect ideas how we could make this possible.

I know it's propably not possible, but I want to stay in my delusion that there is a way to use social media without spitting on my morals.