Then the best I can tell you is that you most likely met many introverts you never even realized were introverts. This is not uncommon since many of us are perfectly functional and even comfortable in social situations even if it's not preferred. As far as the qualities of an introvert being negative I think you've got a bit of shortsightedness going on. Personally, I find many of the qualities of an extrovert annoying but I can also realize how they could be positive. So maybe spend some time listening to others opinions on the subject and try to keep an open mind. I'm not saying you should change your opinions just be open to the possibility that some of what we said is also true.

"The earliest full match known to QI appeared relatively recently in the 2006 book “CosmoGirl!: Words to Live” from the editors of the now defunct magazine CosmoGIRL, and the attribution was anonymous. Boldface has been added to excerpts: 2
“You don’t love someone for their looks, or their clothes, or for their fancy car, but because they sing a song only you can hear.” —Anonymous " -quoteinvestigator.
https://quoteinvestigator.com/2015/12/01/lovers/

Because, people are people. Just because a extrovert has a particular quality it doesn't mean that only extroverts can have that quality. Taken as you've said it sounds like you think extroverts can have the good qualities of an introvert and the good qualities of being an extrovert but introverts can't have any qualities of an extrovert.

It's easier, and cheaper, to just learn both systems and use whatever system is needed at the time.

That's good too.