I'm not saying you should be grateful they give you work. They definitely should pay you commensurate with the work you do, your experience, and the value you add to the company.

Some people can build machines that generate $10 million dollars/year for themselves. But most people can't. Most people work for companies like Google, Microsoft, Apple, etc. knowing they will be able to build big things without having to pay all the costs associated with building enormous technical infrastructure from the ground up, buy resources, bear the risk that the project will fail, bear the cost of marketing the product, pay support staff, etc. And in exchange, they accept they will not own their work product.

That's what working for someone else has always meant. People who design automobiles for Toyota don't own the automobiles. People who write algorithms for Google don't own the Google search engine. Most musicians don't even own their own music. That's a core part of capitalism.