I'm starting to believe that accepting this is a key experience that comes along with being an introvert.
It seems so to me, too. Being introverted is simply less profitable than being extroverted, in a similar way that being good at creative stuff like art is less profitable than being good at logical stuff like engineering. Which is, again, less profitable than being good at social engineering and salesmanship.
If we view career (i.e. profit) as the primary goal in life, then most of us are probably sub-optimal in some ways.
He told me that I would have a very difficult time in my field because of it. He said to expect to feel like I was constantly trying to struggle uphill, just because I am a very introverted person. (educational consulting and leadership).
Ooooo boy was he right. I hate it, but being extroverted would've 1000% helped me early in my career to make connections that would help me later in life.
That being said, I wouldn't trade who I am for the world, and understand that, while I may never make it rich and form a massive consulting firm, I can do good work for the people I do help. And that's okay with me.
This is unfortunately advice along the same lines as "be attractive". It's not something that's fair, and it's not something that's universal, but generally speaking if you're fun and attractive, you'll have an easier time achieving success. That's perhaps a bummer to realise, and again not a universal truth, but for most people it's actionable advice.
I think it helps to have certain traits that are not particularly "introverted". I don't like talking to people and prefer to be by myself, but I'm perfectly content to get up in front of a crowd and teach a class for two hours. It doesn't energize me, but nor does it drain me in any noticeable way. I had horrible stage fright as a teenager and young adult, but it doesn't bother me anymore. I can't say what flipped the switch ... it wasn't practice or exposure, it just sort of happened as I grew older.
What does hurt me is the lack of in-person networking. If people are coalescing into groups and chit-chatting I have no skills at my disposal for breaking into a conversation. And once I'm in a conversation, I find it extremely difficult to keep it going. I hate talking off the cuff and (maybe contrary to expectation) there's only so much you can do to keep the other person talking about themselves.
Later on, I shifted my strategy to closing the gap even more by mutating my personality to a degree I wouldn't have previously thought possible (upping openness and agreeableness in the OCEAN model). That really changed things a lot, though probably isn't possible for some people (it was only a partial success in my case). That solved part of the energy-draining aspect of social interaction, since I now had wiring that made social interaction more natural.
Thankfully, the bar is lower in tech. You can have what would be a disastrous personality for a lawyer or CEO, but still find yourself as the most socially capable guy in the room on a tech team.
The extroverts are the ones who are going to tell you about their success and failure. The successful introverts may keep that to themselves, so even if there are career paths, they're much harder to find without likeminded people who want to be seen as role models.