Most people trying to do this will make little or no money, and the sheer amount of competition and effort required to be the maybe 10% of the top people who can make a living on it is too much for most. And there are less and less structures in place to protect or mitigate risk for them; all Youtube has to do is change an algorithm or demonetize/ban you to tank your streaming business.
And the base assumption now for creative works is "free" and hope people donate to you. A lot of people would make more just working part time at mcdonalds.
What we're seeing is a first cohort of people who get in and build their careers while the niche is still young, and before everyone knows about it. Then there's a much larger cohort of second movers who see the work as aspirational and want to get into it. They have a much more difficult path to success. They have to compete with each other, and with the established players, for a piece of a pie that is no longer growing. Very few end up succeeding.
Jobs where I've previously seen this happen include lawyer, craft brewer, restaurantier, data scientist, academic, airline pilot, and games developer. I'm not sure I see any particular reason to think that it will be different for professional gaming.
And the base assumption now for creative works is "free" and hope people donate to you. A lot of people would make more just working part time at mcdonalds.