I agree with where you start out, but I think a proliferation of partisan platforms would
simply lead to more filter bubbles and more polarization. I would much rather see the Fairness Doctrine reinstated (in the US, anyhow) and expanded to Internet platforms, than to see everyone flocking to their platform of choice, becoming even more oblivious to alternate viewpoints.
I understand your point of view (and used to feel the same myself), but I'd say the last few years has changed my mind.
The way I see it, you either get filter bubbles, or you get miserable people who ditch your platform [subtext: and then the only remaining users are the rage-posters]. And in my opinion letting mainstream platforms rot into a cesspool of rageposters is worse for polarization.
I don't want to see people posting about how rigged the election is, or posting about what bad things hunter biden did, or posting about how hypocritical progressives were this week, or any of the other top conservative topics. I just want no part of it. It's a dead horse to me. If a platform wants to shove that stuff in my face I'm either going to find a way to hide it, or I'm going to leave the platform.
There's a time and place for having debates and seeing others point of view. If we had a proliferation of partisan platforms, I could go to the platform dedicated for open debate, or I could go to the opposing views' platform. I actually do this today (e.g. browsing foxnews if I want to see what's up in conservative-land). But when I'm chilling on reddit the last thing I have ever wanted is to see a trending post near the top of /r/all from the_donald posting some meme about Hillary Clinton passing out and being chucked into a car (this happened on several occasions leading up to the 2016 election).
