I'm not sure I've ever seen anything engineered that is perfect, have you? what even is "perfect"? seems like an unrealistic standard and not the goal at all of any engineered system (civil, mechanical, electronic), I don't think that a good definition of "bad" is everything less than "perfect". I have seen software the fulfills the necessary criteria, especially in the world of control of machines, eg, engine control, industrial control systems, etc. Many things get built that work within their "engineering" criteria. I have one particular software application on a microcontroller that performs various functions and control, I've only ever deployed 1 version on thousands and thousands of devices, it has worked for a decade so far. It went through rigorous review and testing before being released.