One of the concerns I have with the Prime Directive is that it is intended to avoid a "slippery slope" problem, and so it is a very black-and-white rule. Starfleet can't protect a developing civilization from a catastrophic planet-ending disaster... and the core reason is that "interference" can be a bad thing, so we won't ever do it.
There are clearly situations where interference in another civilization would be immoral. There are also clearly situations where it would be moral. We can't possibly figure out those situations and enshrine them into law? We do better today! Homicide is illegal, but there are exceptions like self-defense, and there are mitigating circumstances like causing an accidental death.
Even funnier to think about, is that Starfleet has set the development of warp technology as the cutoff. But there are clearly species out there (Q anyone) who would find that stage of a species development way too early to introduce themselves.
Yes and no. Building such a list of exceptions from general rule can be daunting if not impossible, because you may always get yourself in yet another situation that will need an exception and another, and you find yourself having law that is made of tons and tons of exceptions. I recall the episode where Picard was tasked to help to relocate some inhabitants of planets that was about to be colonized by a rase with a bloated law system and very strict about it. In my opinion this episode showed how such absolutely specific law coinsisting of tons of rules can be used against you. Furthermore moving in such law is also frustrating (we have currently lots of examples with idiotic laws that do not really work because of exceptions list). Like every law Prime DIrective works for "most cases" and just like normal law it is impossible to create it so it covers all possible outcoms and cases.