The antidote outside of ruthlessly moderated special-interest "walled gardens" is a system no one really wants I think. It would need to avoid mechanisms that give community or interest groups powers to promote some content over others. It would need to avoid algorithms that automatically determine and recommend certain content. Other than pruning illegal contributions and obvious spam, it would need to avoid giving virtually any moderation powers to select individuals or the community. It couldn't allow paid promotion or require payment to participate as that merely enables those with greater financial means to contribute and have their content seen.
Introduce any one of these things and the whole system becomes gameable. Within these constraints it seems the outcome would be a loose graph of content tied to known individuals. It would grow amorphously over time, be largely undirected, and lacking the capability of being fully gamed, would probably avoid the attention of marketers and influencers. And probably general users too, since it wouldn't be easy to find interesting and relevant stuff and be quite boring for the average attention span.
The constraints bring to mind the early 90s web which basically had all of these properties. Outside of bulletin boards and UseNet that is. People wanted more convenience, hence search engines became the defacto way of finding entry points into these networks, which caused changes in how these networks presented and arranged themselves, point being even if we designed the perfect ungameable system, as you alluded to if any search engine or aggregator crawled and ranked its content, it would just be meta-gamed into uselessness.
Personally I've come to the conclusion we just have to accept that for the majority of online community-driven content, high SNR is here to stay, and we have to take what value we can individually as it comes. Unless we're willing to forgo conveniences like search, or relevant content recommendations, which I think for the majority of the web is a big old no.
For enthusiasts, building their own walled gardens with in-tune moderation is probably the way to go. Hacker News I think though not perfect is a good example of this, the SNR here is fairly decent compared to the broader web.