It's highly, highly unrealistic to assume 21 year olds earning 100K AND saving 30% of it, have you met many 21 year olds?
I made 36k out of college but now make 135k. I saved 0% at the start and save over 30% now. Assuming I’ll keep getting raises I’ll be a millionaire. My goal was to show OP that you don’t need to start a business to become a millionaire, working in tech for a long career with financial literacy will also get you there.
[1]In general every non-medical degree will get you the same pay as a specialized skilled worker but skilled jobs and manifacturing are even less and often with horrible conditions so everyone goes to the degree route and hope to find somwthing or emigrate. I wish I had done Medicine as my mother said.
The conditions you mention are hazardous but also true for having a career or being materially free in general, rather than just for how to become a millionaire.