That was my thought too. You can absolutely enter the industry, and big players do as the industry becomes profitable enough to sustain more competitors, it's just not available to the average person in the same way the average person can easily compete in the todo app industry.
It's available to the average person if they're willing to put in the work necessary to attract investors. Blake Scholl was a regular engineer before he founded Boom Supersonic. He had made some money on previous jobs but wasn't super wealthy or connected.