I have to hand it to Roddenberry, though; even though having no infighting produces a somewhat-unrealistic show, I think there's a solid justification to have the rule anyway. It prevented TOS and TNG scripts from being caught in tension between trying to "say something", vs. entertaining the audience with "low" soap-opera drama (of the kind you see increasingly in the later series.)

I have a feeling this might be no small part in why TOS and TNG are the two ST series that contain 90% of the "only comes up once" sci-fi plots / concepts / worldbuilding that people ever make reference to when talking about "things from Star Trek" rather than when talking about Star Trek. TOS and TNG, while definitely soft sci-fi, were to some degree trying to create 22-minute-long works of literary Speculative Fiction, modelled after the sort of things you'd read in serial SF magazines of the 1950s. Later ST series are emphatically not that, and nor do they try to be.

Eh, it's the writing and the characters that make it fly, not the budget. TOS was blessed with some really good writers, and was very lucky with the actors.