I think people are much more complicated than the simple introverted / extroverted. I’ve personally come to the conclusion that very few people really fall exactly into either category and most people just seem to be a semi-random assortment of traits associated with one or the other. It’s really difficult to disprove things that don’t exist but I feel like the two categories aren’t an accurate descriptor for most people.

I think the problem here is the traits associated with one or the other, not the two categories themselves. Perhaps if you read different definitions of the two, you'd think differently as well. The traits addressed in the article specifically seem particularly fluff.

I believe that while any person can easily use introverted or extroverted capacities, all people have a baseline or more natural/habitual behavior.

I think that’s true. I’ve met a lot of girls who tell me they are introverted or extroverted but the only difference between them is whether they are anxious or not around people they don’t know well so I’ve come to think that the other traits people seem to associate them are just kinda arbitrarily clumped together but I could totally see how you could define them differently and have the categories actually make sense.