You can use "if" to spin any scenario you please. But you might not want them to meet, say, Captain Picard or Captain Janeway, sticklers for Starfleet protocols, who would be armed with the Prime Directive. Those captains might well have left them twisting in the wind without batting an eye.
What makes the argument moot for me are a few things:
T'POL: The Vulcans stayed to help Earth ninety years ago. We're still there.
ARCHER: I never thought I'd say this, but I'm beginning to understand how the Vulcans must have felt.
It's interesting to see the boot on the other foot. Archer gets a bit of context regarding the Vulcan guidance humanity has been receiving and what a responsibility that was for them. He's conflicted, he's a hero through and through and of course he wants to help. See this (
bolded emphasis mine):
ARCHER: The hell with nature. You're a doctor. You have a moral obligation to help people who are suffering.
Archer hangs Phlox out to dry over his reticence. Then:
PHLOX: ... Forgive me for saying so, but I believe your compassion for these people is affecting your judgment.
ARCHER: My compassion guides my judgment.
Archer's decisions are led by his desire to help. He's the most puppyish of the Captains at this point. He wants to say "How ya' doin buddy?" to literally everyone he meets. This is given further context in the 'Prime Directive speech when Archer says:
ARCHER: I have reconsidered. I spent the whole night reconsidering, and what I've decided goes against all my principles. Someday my people are going to come up with some sort of a doctrine, something that tells us what we can and can't do out here, should and shouldn't do. But until somebody tells me that they've drafted that directive I'm going to have to remind myself every day that we didn't come out here to play God.
Which is the crux of the dilemma, tying back to what Phlox said:
PHLOX: If the Menk are to flourish, they need an opportunity to survive on their own.
ARCHER: Well, what are you suggesting? We choose one species over the other?
PHLOX: All I'm saying is that we let nature make the choice.
and:
PHLOX: What if an alien race had interfered and given the Neanderthals an evolutionary advantage? Fortunately for you, they didn't.
And that's the dilemma. They are explorers, but there is a line that is difficult to draw. They've known these people for two days at most and do they have the right to disturb a natural process? That's why I mentioned Kevin Carter and nature-documentaries. If a cameraman films prey being hunted and killed by a predator, does that mean that the cameraman did the killing? That's at least part of the debate that the episode is meant to stimulate.
Honestly, to watch the episode and come out with the opinion that either Phlox or Archer are villains would require a person to close their ears to pretty much everything that's said in the episode. It's not a case of "fuck 'em, we could cure them but we'd rather let them die". Phlox is cut up about it. It's very clear in the scripted words and the performance choices Billingsley and Bakula made that it's not an easy decision for them to have come to. Similarly Archer.
Tellingly, T'Pol is largely kept out of it, perhaps because this stuff from her character may come over as perfunctory and cold, but Archer and Phlox... it's tough on them. It's something that they have to wrangle with and it's something that as explorers they haven't come across before. Surely that's the point of the show.
Finally, yes. A non-warp capable civilisation? Picard would have flown on by without a second thought.
Luckily for you, this is just a TV show.
Well, yes. I've been aching to point out that it's a TV show so nobody died. That should allow us to discuss the actual themes of the episode in the abstract without bringing hyperbole into it.
Speaking personally, if I were in Archer's shoes it would have been my instinct to help. But that's me making a decision as a university lecturer. If I had to make that decision as a Starfleet Captain in terms of giving them warp-drive, potentially holding back the Menk, or generally just sticking my nose in where it doesn't belong... I don't know. A Captain shoulders a lot of responsibility. Maybe I would have done exactly the same thing.