So basically the prime directive was invented by another culture and everyone in the galaxy recognised its importance and played ball.
It's just that - for some reason - Starfleet are the only ones who bang on about it like they're the only people in the universe with the morality and intellect to embrace such a high-minded ideal. Or is it the humans? Bolian crew members sit there thinking, oh look, the humans are patting themselves on the back for "inventing" the prime directive again.
It's like when humans go on about Cochrane inventing warp and all the aliens onboard who had warp centuries before humans just roll their eyes.
Nope.
(I might be misreading you?)
The Prime Directive and Interstellar Law are two different things, and we have no idea when either of them were invented (Well we know when Starfleet's Charter was drafted, or at least we did until Enterprise fucked it all up). Hell, the Prime Directive is not even a human law or a Federation Law, it's not even a law. It's a regulation of Starfleet. Logically if you're not in Starfleet, even if you're human, but an immoral person, you can #### up and rape any worlds, culturally or geologically, which you feel like, if you have the power to do so, and you got a firm handle on who might be miffed by you asteroid-fieldifying heavily populated planets, and try to do something about you.
T'Pol spent a couple episodes trying to teach Archer about not interfering with prewarp cultures, or helping less advanced races out of a pickle and into a blender. So yes the Federation, and before that "humans" inherited the Prime Directive from the Vulcans who had been in space for half a million years, and who had just spent a century trying to make sure that humanity didn't blow itself up as it "invented" and used antimatter to make warp reactors despite being bared from openspace by their pointy eared overlords. If you start helping a dullard, you need the stickitudity to keep helping that dullard until their wits pick up enough speed that they don't need help anymore, or there was no reason to start helping the imbecile in the first place.
If you can't commit to the long game, don't commit.
Think about it, in the real world if you help someone a lot for a weekend to clean their house, and they become accustomed to that help, start to depend on that help, and have no idea how to maintain that degree of "helpededness" (I had to ruminate about that one.) they're most likely going to backslide and feel sad, or push on and fuck up by trying to do the work of two or three people when they are only one person.
Other alien races have no requirement not to use their less intelligent neighbours as resources to be tapped and used up... Of course, if they do that enough, someone is going to stand up eventually and punch them in the nose. Acting like an asshole lets people treat you like an asshole.
The Prime Directive and what we know of interstellar law seems to be "the Golden Rule".
Treat others as you would have them treat you.
Basic shit, yeah?