I watched a review of the TNG episode "Thine Own Self" a while ago where it was mentioned that Picard doesn't appear until the very end after Data gets back to the Enterprise, after all the scenes of Crusher having the bridge and Riker observing Troi taking the test to becoming a commander. They suggested that Patrick Stewart may not have been around for most of the filming but they needed him to appear at least a bit in the episode because it was in the contract.
Is this a common thing? Yesterday I was watching DS9's "Paradise Lost" and couldn't help but notice that Bashir only has like 3 lines on the Defiant and could easily have not been there. But Quark doesn't appear in the episode at all.
But if Armin Shimerman didn't need to be in every episode they could easily have cut him from the episode "Duet" because the only line Quark has is him wondering whether Bajoran survivors of a labour camp like to gamble.
Maybe I'm just thinking too hard about what happens behind the scenes instead of just enjoying the show.
I definitely have issues with the episodes where they decide it's better to let civilisations die than interfere, if it were up to me they'd be retconned away or at least rewritten.
But in general I think it's a good idea, including not interfering with the politics of other space-faring civiliations. The Federation respects life but it also respects culture. The prime directive relates to the latter. Having the development of warp technology as the cutoff point for no interactions at all kind of makes sense since it allows those societies to develop a unique culture of their own. Letting civilisations die is silly, having a slightly interfered-with culture is better than no culture at all, unless perhaps the people within that culture would rather it die.
I see the prime directive as a way to prevent imperialism. Being on good terms with other cultures is one thing, but being on good terms because you've interfered means something intangible has been lost about their society and culture.
I also consider the fact that everyone thinks they themselves are the "good guys", even people who do bad things. If the Federation just abandoned the prime directive every time they thought "oh it's the moral thing to do this time" then they may as well not have the prime directive at all.
Think about it this way: you come across a society that believes in sacrificing innocent people to the gods. Is it okay to interfere to prevent the loss of life? But what if it was the other way around and you were the smaller civlisation and a large empire that believes in sacrifices finds it abhorrent that you don't sacrifice anyone, and tries to force that culture on you?
I'm not equating not-sacrificing and yes-sacrificing as moral equals, that's just an example to demonstrate that the action of the interference by a larger society could be dangerous. If we interfere because it's "the right thing to do" we run the risk that in a couple of hundred years' time our own culture has progressed to the point where we consider our previous beliefs to be wrong and that it was wrong to force smaller cultures to adopt them. I'm sure you can find examples by looking at real life empires vs. what the modern versions of those countries now believe.