Nothing wrong with saving a "primitive" planet as long as you do it discreetly, and don't set yourself as gods or emperors afterwards, or provide advanced tech to cultures that aren't ready for it yet.
The TOS version of the PD is more of an anti-imperialist thing than a strict "hands-off" policy where strange new worlds and civilizations are concerned.
Or, to borrow a line from Futurama, "When you do things right, people won't be sure you did anything at all."
That's the Lloyd Biggle, Jr. version of the Prime Directive. Biggle was a science fiction/mystery author, mainly active from the '50s through the '70s, who wrote a number of stories about an organization whose version of the "non-interference policy" was that you should interfere to guide other planets toward a more mature civilization, but you had to do it subtly and in secret so that they didn't realize you were doing it. Which is also basically the Gary Seven approach.
Although that's still quite problematical -- who are we to assume that our form of civilization and progress is right for another species, and what gives us the right to manipulate them into developing the way we want? Saving them from disaster is one thing, but "guiding" them to be more like us is still deeply imperialistic, no matter how secretly it's done.