> The font size itself should just be how big the user wants the text which in turn will depend on the user's eyes and viewing distance etc.
So software "pixels" are relative units now, but you would have them get larger or smaller as the user moves closer to or further from the screen? (I think I'm not quite getting it, sorry.)
We're wishing for a screen with such a high pixel density it makes pixels a completely irrelevant implementation detail of the screen itself. So nobody would be setting their font size (or anything else) as some number of pixels, they would in fact set it in a real physical unit like cm/inches and that choice merely comes down to personal preference, eyesight and how far you are from the screen.