Is the Prime Directive Just?

The Sentinelese tribe make their home on North Sentinel Island, India. They're named after the island they live on, because nobody actually knows what they call themselves. In fact, generally speaking, nobody knows much of anything about them. After they survived the 2004 tsunami that swept right over their island (another thing we don't know: how the hell they managed to do that), we sent a few helicopters over the island to photograph them and make sure they were still around.

Well. You make North Sentinel Island sound like a Zoo.

Nonetheless, I doubt that the Sentinelese, although living what we might regard as a very basic existence are wholly uninfluenced by technology.

I bet plastic waste washes up on North Sentinel Island too.

That actually isn't a bad analogy. It is about as close to a human zoo as anything I have ever heard of, and as close to an example of the prime directive in action in the real world as I had ever heard of too given the laws regarding contact with the locals.

They really are pretty unaffected by technology. No vaccines, antibiotics, etc. No climate control... water sanitization...

I'd say it isn't always because sometimes going against it would be more likely to minimize suffering.