The point is always this: can the culture handle it? In Homeward it is made very clear that as soon as the people found out about the Enterprise rescuing them, it would destroy their culture for good. Same thing happened in Who Watches The Watchers. Same thing in Pen Pals. The civilizations could not handle alien contact. So either rescue them without letting them know that you rescued them, or let nature follow its course.
Um... in Pen Pals
, we see only a little girl who seemingly had no problem with alien life. Your painting every culture you've mentioned with very broad strokes.
I can't believe the people who claim that extinction is somehow better for a species than cultural contamination. That just boggles the mind.