How can you win if plan values are nearly always negative
Just ignore the plan value entirely and only use your own judgement. There is very little correlation between the value and what will actually work. The AI relies on it though, which is one of the reasons it makes such bad decisions.
You'll just have to forget about things in a game being done to a certain standard of quality. Because otherwise this game would not have been made in the first place. Expect the unexpected.
It is best to avoid words like "broken" altogether around here because anything perceived as combative only galvanizes Paradox supporters, detracting from the substantive discussion. You won't change any minds - much less of the developers - if the discussion looks very controversial, even when the controversy is mostly about your tone.
By the developers' definition, something is only broken if it does not match their design. And you should not confuse what you hope or could reasonably expect the design to be with the actual design.
"Reject reason to make the impossible possible!" - podcat