It's too bad, I think idea of organizing a social network based on proximity and centered around community information is a viable idea, It's just that NextDoor is doing that with our worst instincts.
NextDoor and Craigslist and Reddit's /r/{city} communities just prove that it may be viable but it's pretty undesirable. I think it's best to not give the most neurotic, ill people of your community the loudest voice, but these social networks also create this neuroticism and illness.
You also create a scenario (NextDoor especially) where all the sane people are driven out by the crazies. Back when NextDoor was new, after a year it would come up in conversation and sure enough, anyone normal would admit they tried it and had to delete it.
Social media is messing us up. I don't think we're missing some new take on it that's going to make it all better. I think the vestigially tribal parts of our brain make it a non-starter. We need to get back to the face-to-face -- it seems to be the only way we keep in mind that there's a human at the other end of the line, not some nebulous automaton that we craft into everything we hate in the world.