I think that Insurrection is a decent film. Not great, but not terrible either. I watch it every now and then.
It is mentioned in the movie that the normal regenerative effects of the planet are not enough to reverse the aging of the Son'a. That is why the Son'a want to collect and concentrate the material from the planet rings.Band why didn't Starfleet just come out in the open and cut a deal with the Ba'ku and Son'a for use of half the planet as a heath spa or something, anyway? It's not like 300 people are going to be bothered by a Starfleet medical facility for treating people's ailments that could be located on another continent
Actually it was said that the normal regenerative effects of the planet would take at least 10 years to affect the Son'a.