when I learned it was common for a founding engineer to get like half a percent of the company, I was appalled. I'd rather just start my own startup

I don't think people appreciate how hard it is to go from 0-1. To validate a product/market, get initial customers, before raising, heavily derisks the business and 1% is fair. Sure, you could just start your own startup, but you'll have to go through the brutal glass eating process of doing exactly that, starting a company.