I argue that by your own ideal state of decentralization, the current system should be working perfectly fine for you regardless of private companies censoring X, Y, and Z.
The "fully decentralized" internet can (does?) already currently exist today alongside our usual youtube/facebook/cloudflare/etc centralized internet. The state of centralization is entirely by user choice, not by force.
Literally the only necessary component for a decentralized internet is net neutrality - that packets are delivered without systematic blocking or throttling on the basis of content. And net neutrality, while in danger, hasn't AFAIK devolved to blocking sites for objectionable content (not yet in the west anyways)
In other words, theres a very clear answer to your conundrum of "at what point do we accept that we have different viewpoints and live and let live?". Regardless of political views or whatever else, your content ought to be routable on the internet. Everything else that we as a society have built on top of that (edge caching, content platforms, delivery systems, heck throw in DNS while we're at it) are unnecessary for a decentralized internet, so if you piss off society and nobody wants to do business with you, maybe it's fine if you're on your own.
Of course, you also argue "there are problems that people have, and things that need to be talked about, but they aren't allowed to say anything about it". That's an understandable position, but should be considered unrelated to the issue of centralized vs decentralized -- I would still not want to argue with some race-baiting troll, even if I hosted my own content instead of uploading it to youtube. I would still ban them, ignore them, blacklist them, or whatever options exist in the decentralized internet.
>The societal norms are shifting to a place where there are certain topics that are not allowed to be discussed at all even if looking at them from a critical lens
This isn't really any different from the majority of human history. Private speech - available through a text message or a DM - is still pretty unregulated (and likely will remain that way - for example iMessage is end-to-end encrypted and I suspect any chat service that moderates private messages would run into issues maintaining users). Public speech has always been heavily regulated by those who hold power - whether it's the FCC regulating TV content or being snubbed from the community when you advocate a particularly unsavory opinion at a town gathering.
So then maybe the problem is that more and more of our speech is "public speech" (like a facebook post) and not "private speech" (like a facebook direct message), and hence in practice more and more speech is being censored. I could agree with this. But that's neither a centralization problem nor a censorship problem.