There's definitely a middle ground with tropes, but I think it's also era dependent (and likely cyclical). Some tropes have periods in time when they come into heavy use because people are enjoying them (or there's a new twist to be done with new technological, cultural or social changes), and then become overused a too "tropey" because everyone starts recognizing them. I suspect there may have been a different level of acceptability to some of those tropes (or those tropes in that genre) at the time that series first aired, possibly because of a dearth of good science fiction on TV.