a twitter-like platform needs a big central algorithm that can associate posts with certain topics and interests to be able to serve up an interesting feed

I grew up on Tumblr and it thrived for the longest time with a chronological timeline.

most people are just kind of shouting into the void and that endless storm of posts has to be filtered and organized somehow

Yes, it was done through tagging. Notably, tags in Tumblr didn't have to be inline.

Tagging died on Twitter because the inscrutable blackbox of the algorithm made people unsure if tags actually improved the visibility of their posts or not, there's some folk-wisdom that suggests excessive tagging leads to deboosting of your profile, since it could have been considered spammy. Also, there's only so many characters in a Twitter post and sometimes there's just not enough left for relevant tags.