It's almost impossible for an Introvert to become a fully Extrovert, this requires a lot of "work" and suffering and I see no reason for someone to strive for it. "Extroversion" simply drains our batteries, period, how much of it we can withstand is another story.

It's impossible because nobody is a fully introvert and nobody is a fully extrovert. We are all a blend depending on the situation. Introvert exclusive and extrovert exclusive is a culture meme. You are online all day talking to people. You are not an introvert.

It's not different, you claim that everyone can run with the same pace, you neglet the fact that for some groups of people this activity is much easier and for others it's harder, a lower BMI group like those with GS can run 10km with less effort. When you ask from everyone to "run at the same pace" you have to acknowledge that some groups are strugling to do that, it's not easy for them and it has nothing to do with "how much they try" obviously they try and they strungle more than those who seem to outperform them.

I don't claim everyone runs with the same pace. I claim that people sometimes run fast and sometimes slower and that this is not a race or a competition. Again, false example. You use physiology. I use situation related example. Again, someone who talks to 100 people at a party is the same as you who talks to 100 people online.

Of course there can be some variations through life. Genetics and our environment is what I think mostly determine us,

well, this is all there is to the equation..

we can try to change part of our environment but we can't do much about our genes.

thing is there is no scientific basis that genes make you an introvert or an extrovert. In fact, there is no scientific evidence that at all that is falsifiable and replicable because the dynamics are so fluid.

it is a cultural meme. nothing more, nothing less.