We could make a public platform. In the US this all but guarantees a protection from censorship. Third parties could offer moderation services. The brave could suck on the firehose!
The funny thing is that Usenet is already a highly censorship-resistant platform, and tools like NoCeM would let you subscribe to third party moderation streams!
I genuinely forget Usenet is still technically around these days. I dabble in the idea of using it here and there, but the ease and convenience of the modern www has spoiled me quite a bit. If I go to a decentralized platform, it's more likely to be something fediverse.