People are incredibly mean and nasty to each other on nextdoor in my neighborhood, and they literally live down the street from one another.

You're completely right, it's not anonymity that causes people to act like this, it's the fact that we as humans can't perceive text on a screen as another human being that activates the empathy center in our brains. Coronavirus has made this 100X worse as people are losing their humanity being locked away from everyone else.

I've had some of my best social interaction recently on VRChat of all places as it gets the closest of anything I've found so far of making it feel like there's actually a human being in front of you.