What specifically is wrong with it?
Jack had (I assume) something that was 100% his in the beginning (or his and Jim McKelvey's - I don't know the story). They built something of value. They gave parts of it away, as well as cash, to people in exchange for doing things for them. Over time, the company that he owned continued to gain value, because people were willing to pay money to that company for the service it provided. At each point, every customer they served and every employee they took on presumably thought they were getting a good, fair deal. (If you're not getting a good deal, don't do business with someone.) At the end, the thing he owned was worth $1.5B.
What should have happened differently? In some alternative universe, perhaps everyone all along the way, every possible employee, could have demanded a larger percentage of the equity in return for their labor. But they didn't. I don't see why it's necessarily reasonable to, from the outside, say that anything is wrong, and reach in and start redistributing wealth. People can probably become billionaires today more easily because technology scales better than in the past, and because there's an investment environment that supports it.
Imagine I found a company solo. All by myself. I provide a service that lots of people are willing to use, and they're willing to pay me for. Maybe I've cracked the problem of Strong AI, and I'm selling my AI's services. It's software, and it scales well, so before long my company is worth $1B. I'm still running the company all by myself. How should it play out? If I brought on an employee at some point as a sysadmin should they automatically receive a percentage? (If they negotiated for that, then yes, otherwise no.)