There's a nuance here that you're missing - self-curating your social media experience is vastly different from the algorithm hellhole that is the modern corporate social media landscape. You can filter out any dissenting opinions or facts, but you can in real life, too. And like in real life, it takes a lot of active effort to get to that point. Whereas the algorithm will do that for you without you even knowing it.

I'd say that self-curated social media is like going off to college or moving to a new city while the algorithm is like living in the town you grew up in. I grew up in a very liberal state, but there were about 3 non-white kids in my entire high school the year I graduated, and it wasn't until I was introduced to Tumblr in college in the late 2000s that I first heard words like "transgender." And Tumblr is the most self-curated social media that I've ever seen. Back then, you couldn't even follow hashtags - just people. So your front page was exclusively people that you followed and the posts that they reblogged from people that they followed.

You don't have to use filters, just like you don't have to subscribe to subreddits on Reddit. You can just use the default front page if you are afraid of tailoring it to your tastes.

That explains the age demographic

Not sure if a third is everyone