I was worried about getting fired at these sort of places until I saw how they behaved when I quit a few of them.

A startup that is firing engineers on the spot who dare to disagree probably won't last much longer anyway. Best of luck with their "critical" deadline then...?

Or you just miss promotions, raises, bonuses because you didn't do enough, "moderate impact"

Then the startup has to ramp up a hiring pipeline to backfill or dump the work onto someone else. Either way they won't get what they want.