The other problem with Slack is that it just straight up... doesn't do what you tell it to. I have a set of notification settings that work for me. Slack goes ahead and just does something else, and you simply can't fix it to do what it's told. (Or couldn't, anyway; I've been off Slack for a while.)

Absolutely agreed.

How much time must everyone be asked to waste to “tune” a working set of applications to something reasonably sane for human beings.

Sure, what is sane for one human might not be for the next, but it’s not as if trends cannot be discerned.

How ridiculous would it be to be told “if you don’t want people constantly barging into your office, lock the door”?

It wasn't much time at all. Honestly, the push back on this always baffles me.

And when I had an office, I closed (not locked) the door to signify I was in a focus mode. I don't get your point.

The idea that software like Slack could be setup as "one size fits all" is just ludicrous to me. We have options because different people require different settings.