Over the last 16 years of my work I've noticed that the people who are being promoted are mostly (not all of course) the mediocre ones, who like to talk and make good impression (however hardly making any good work - they are just selling this as good). But they make good impression of how great they are (unfortunately they use lies to proof that, but seems like nobody cares).
A couple of jobs ago the whole management was made by the guys who were petting the boss, and were going out to pub with him. I wasn't. I hate crowded places, and insincere people. When the boss was lying about my work in my half year review, no one from the management said anything. When I was fired because of that - they were afraid of saying anything. They were talking with me that it's not fair, not with the boss. And frankly, I'm really grateful for firing me.
Now I'm still an introvert, however I have wife and kids, and I have to be more open. However only to them.
I'm working remotely as a consultant, so I have no real chances of any leadership promotion. Working remotely is great for people like me. No promotion it not. However the job pays my bills, which is also quite important.
So overall: it's harder, seems like people care more about the impression, not the employee real work.