I contribute to Askhistorians occasionally, which specializes in long form, long term answers in response to queries. It's a useful thing, but the "value proposition" as it were fundamentally relies on having large numbers of readers to attract subject matter experts and users with interesting questions. I've experienced everything listed.

With that said, none of it matters because the model breaks down without the userbase. You can't move to an alternative because the historians aren't there, even if the questioners are. Even if you convince a subset of them to move, churn will eventually kill it anyway. The whole thing also needs to broadly in the flow of mainstream internet culture to make it useful.

So what's the alternative?