Even on the high end, there were only 11 books that sold more than 500,000 copies.
If I can spend two to three years writing a novel and my best case scenario is having it sell a couple hundred copies
Isn't the best case scenario here that you are the top-selling author, selling over a million copies? I feel like the author of this post is just assuming that they are not that great a writer, that they cannot reach the top 1% of their profession.
Writing books is like making video games. Many people dream of creating one, and the vast majority of them are pretty bad. Nevertheless, some incredible books and video games are created, and the stars make a lot of money. Writing books may not be a good idea if your plan is to write some average books and make an average amount of money, but if you think you can write an amazing book, then what else can really compare?