My usual experience flying between the UK and Europe and in three cases China was that 2 hours has always been sufficient before departure and that 1 hour is about the limit after landing.
If I decided that from now on, I'm only walking to and from airports rather than driving or taking transit, does my multi hour walk to the airport make it so that airplanes are now as slow as driving places and therefore not worth it for any domestic flying? No, that would of course be a ridiculous conclusion.