No, I am sorry, this aphorism may only be defended in those instances where poor planning results in a situatiion where insufficient time is available for any planning, and events now dictate action. In which case, what right does the 'good plan' have to be called a plan?

Consider Eisenhower:

In preparing for battle, I have always found that plans are useless but planning is indispensable.

Other humans must be interacted with in real-time. Consider a non-military analogy: a good comeback confidently issued now is better than a perfect comeback issued next week.

It also works for computing. Consider languages which have a REPL to those that don't: for many applications, good code executed now is better than perfect code executed next week. This is often because requirements change over time, and the future cannot be predicted- the customers won't know what module they want next until they've used the current module.