Here is the thing though: Rules need to be codified. And the application of this code -or law - in fringe cases - that's IMO the truly interesting stuff! A typical prime directive episode SHOULD be: The PD forbids us to interfere. How can we help regardless without breaking it? Other cases: The Klingons have already broken the PD - do we ignore or try to reverse their interference? How far are we willing to go? Instead most episodes go the stupid "do we help our dont help?"-route. Which is trite - if the menace is external (other aliens taking over, space phenomena threatening the while planet,...) you help, if the problems are self-made (dictatorships, war, famine...) you don't help, except after being specifically invited to do so. And you don't give planner-threatening technology (warp cores, anti-matter) to people that weren't able to discover them on their own. There's just no meat in arguing such standard cases.