Sounds about right. There is no real introvert or extrovert. Just people who like hanging out with and people we don't. With people whom we like to hangout with we are extrovert, and other then we are introvert.
This is remarkably reductive. Some people -- including me -- would prefer not to hang out with anyone, including people they ostensibly like. For some, the scope of people with whom they'd be comfortable hanging out is quite low. If we can't call such people introverts, then I don't know why we bother making up words for things at all.
Introversion and extraversion are very robustly defined and proven traits. Maybe you don't understand what they are, or maybe you're one of those people who's not strongly one or the other so it seems to you like "everyone" just has both of those, but there is no real question about whether the traits exist.
How would you react if someone came in and said "there is no real gravity; it's just that the earth loves us very much"? Or "there are no viruses and bacteria; we get sick from bad air and evil spirits"?
That's more or less the level of wrong that deepstack is. The Big 5 Personality Inventory is probably the most robust, reproducible piece of psychological science we've got, and while there might be arguments that it needs more nuance in places, the bare existence of introversion and extraversion as traits is not even slightly in question in the scientific community.
Your feeling that it might not be true—or that I'm "overly confident" in its truth—just doesn't hold up to decades of scientific consensus.
>How would you react if someone came in and said "there is no real gravity; it's just that the earth loves us very much"? Or "there are no viruses and bacteria; we get sick from bad air and evil spirits"?
Gravity can be measured more objectively than social science (such as psychology) concept such as introvert/extrovert, which is determined by committees such as DSM IV or maybe now V. Introversion and extraversion are just one thing that is measured within a certain context.