AI proponents completely ignore the disparity of resources available to an individual and a corporation. If I and a company of 1000 people create the same product and compete for customers, the company's version will win. Every single time. Or maybe at least 1000:1 if you're an optimist.
They have access to more money for advertising, they have an already established network of existing customers, they have legal and marketing experts on payroll. Or just look at Microsoft, they don't even need advertising, they just install their product by default and nobody will even hear about mine.
Not to mention as you said, the training advances only goes from open source to closed source, not the other way around.
AI proponents who talk about "democratization" are nuts, it would be laughable if it wasn't so sad.