> most people just have a very hard time declaring “this person is worth 0 additional seconds of my time” and actually following through.

I think that's what "setting boundaries" is about: Standing your own ground, and decide: "Not worth my time and energy.", yet still believe in the good in people. I think even bad people have something good in them. It's just not healthy to figure it out for me, once the manipulative (or bad) habits have surfaced.