I watched INS a couple of weeks ago, and that definitely has some major holes, specifically to do with the Ba'ku:
The Ba'ku settled on the planet 309 years ago. They have a death rate of zero, and seem to have no qualms about having children, but the population is only 600. If they started with only two people, and each couple had two children every 33.3 years, the population would be 1024. Maybe there is a periodic cull they neglected to inform Picard of?
Despite the Ba'ku's rejection of technology, they would have needed technology to exile the So'na. Either using a ship to take them to another planet, or using a communication device to convince a ship to venture into the Briar Batch and pick up the exiles.
(Also, despite the rejection of technology, they identified Data as a positronic device and attempted to repair him.)
SOJEF: A century ago, a group of our young people wanted to follow the ways of the offlanders. They tried to take over the colony and when they failed...
RU'AFO: And when we failed, you exiled us to die slowly.
Ru'afo makes a fair point. They tried to take over the colony (no suggestion this attempt was violent), and in response were given a literal death sentence. To exile them off-world when there are no more than 600 humanoids on the entire planet seems unreasonable. Why didn't Picard point this out?
Why do the So'na need the Federation at all? The Briar Patch is a no-go zone that no reasonable person would enter. The Fed are new to the area (note Dougherty's line about not having fully identified the anomalies yet). There was nothing stopping the So'na carrying out their operation on their own - except that the plot required the Federation to be there.
And again, it's a big planet with a population of 600. What's stopping the So'na from setting up their own colony elsewhere on the planet, and enjoying that sweet sweet immortality with the Ba'ku none the wiser? Unless the space hippies have advanced satellites in orbit to warn them of such an incursion...
Finally: another inconsistency in the Ba'ku's rejection of technology - the massive hydro works that enables Data to lower the level of a large natural-looking lake by turning a metal wheel which is presumably attached to a massive concrete dam.