I don't know what to tell you at this point other than 'eppur si muove' -- you're giving me a bunch of theoretical reasons as to why you think it
shouldn't work, and yet Gemini
has been around for years now: it
is maintaining itself as a distinct niche; it
is not full of spam, ads, or slop; its content
isn't readily accessible from the web or turning up in major web search engines despite the fact that there already are multiple web gateways around; and it generally
does fulfill the intentions of the people using it.
You're treating this like a hypothetical discussion, but we're talking about something that already exists and functions.
And I don't think the "hobby" distinction you're making is particularly relevant, because the whole point of it is again to function as a community of amateurs -- and it's doing that quite effectively.