I think the mainstream does care about decentralisation, but only in so far as it affects the final experience. Censorship on major social networks is a great example. People absolutely do care, but starting their own Reddit (for instance) is far outside of their abilities. Where would you even begin?

They also don’t care about how it is implemented, just so long as it works. Sometime I feel like the HN crowd cares more about what language a product was written in than how well it serves their needs!

What is required is a platform which combines the UX of a centralised service with the ability to easily spin up new instances, is open-source, security audited, etc. etc.