I think your gut is right-on; the issues you describe aren't just endemic to BigCo, you'll find them anywhere and everywhere...but...if you have the financial risk tolerance to work at a startup, why not start your own company instead? These days, it's really easy to get going and self-fund with very little capital if you can save up living expenses & tighten the belt for a year or so.

Set goals and a drop-dead date (i.e., if I'm not making money within $65_percent_living_expenses_depleted, time to head back to work) and I suspect you'll be happily surprised by the outcome...