Field of View as has already been mentioned (as focal length) changes the relative size of features due to the relative amount of foreshortening
Also, I think for myself, I tend to make all manner of derpy or weird expressions that cameras capture, made worse by like trying to smile awkwardly and reacting to camera flashes and clicks, whereas in a mirror or even video what is seen is more the more normal collection of those expressions that just looks kind of like a living, moving person.
In addition to what you said: I have the impression it has a lot to with how cameras capture a single instant, while when looking in a mirror you see yourself moving naturally: Even if you watch a movie with the most handsome actor they will look absolutely ridiculous on at least HALF of the frames you pause it on. But you don't notice when it is part of a fluid movement.
Do you remember
https://i.imgur.com/nO54muO.jpeg? Exactly the same thing in my view.
And finally it is always how you perceive yourself and how other perceive yourself: I'd say most people would rate most of their own pictures lower than everyone else.
