If this was a hardware or software issue it would be obvious that you're trying to scale systems that do not scale.
In technical terms, social "algorithms" are O(k^n), exponential.
You're trying to do the impossible, eh?
(Really, the argument could be made that FANG et. al. are becoming a new de facto world government. From that POV you're attempting to solve the hardest human problem, eh?)
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No one is forcing you to be that big. At the end of the day, scraping away all the bright-eyed rhetoric about "connecting all the people, places, and things for great good", you're doing it for money. Building a moderated social network isn't impossible (maybe) but it's woefully expensive.
The existing systems are, arguably, harming people and messing up society, tech companies notoriously have a lot of money already, but are unwilling to prioritize and pay for the moderation that could (arguably) improve things.
So... what? I don't have any answers, I just want to point out that from my POV the problem is clearly hubris and basic cheapness.