I think that science fiction does not age well. Part of the appeal of science fiction is the novelty of it. We get drawn to science fiction programs because of the promise of something new and exciting. If the science fiction is not of great quality, the promise of something new and exciting can keep us watching. So I have a theory that any science fiction older than the year 2000 is not that interesting anymore.
I have been rewatching Star Trek Voyager and Star Trek Enterprise. I think that Star Trek Enterprise is the best of the Star Trek TV series and worth watching again. I love the characters on Voyager, but the writing in the first two seasons is tepid. I think that maybe the show gets better later when the Borg show up.
I have tried to rewatch Star Trek Deep Space 9 and Star Trek The Next Generation. I love the characters on Deep Space Nine, but the show is too episodic about things that hardly seem interesting anymore. The show has an overall story arc, but they don't pay much attention to it. I am going to go back Star Trek The Next Generation at some point, but by now the series is feeling really dated.
Compare the old shows to some of the really good science fiction shows that have come out since 2000. For example, LOST, Battlestar Galactica, Colony, Star Wars The Clone Wars, Star Wars Rebels, The Expanse, Dollhouse, Tru Calling, Smallville, Firefly, Life on Mars, Doctor Who (2004 version), Torchwood, Farscape, Stargate, Stargate Atlantis, Stargate Universe, Dark Matter, Heroes, and The Last Ship. Also, Buffy the Vampire Slayer had just a touch of science fiction in it, and it remains one of my favorite shows because on rare occasion the show is incredibly brilliant.