Oh, these were fun descriptions and discussions.
Since it has been evolving and different folks use it different ways, I echo rachy and some others who include an emotional component or something that pulls someone else in , or is intended to, or to get attention in either a positive or negative way. So I would
not typically use it for just a mishmash outfit, for example, or someone just having a bad day, though I might, or hear otgrst, referring to self as hot mess to make light, or fun, but not REALLY.