Sliders actually rebounded when it moved to the Sci-Fi Channel for its last two seasons. By the back half of season 3, it had become one of the most unwatchably awful shows I've ever seen, an incoherent mess by incompetent writers who thought that science fiction meant ripping off old B-movie plots and that character conflict meant gratuitous petty bickering. The third-season finale was so horrifically awful that forcing someone to watch it could constitute a war crime. (Though it's not quite as bad as the series finale of M.A.N.T.I.S. from the same network two years earlier.) But when it moved to SFC for season 4, it brought in an almost completely new writing staff consisting of people who actually understood what science fiction was and how characterization worked, and it actually became good once more -- still with some notable flaws, but better than anything since season 1. I've never seen a show degenerate so far and rebound so strongly.
But you're so right about SeaQuest. Its first season wasn't great -- there were only two episodes that I really loved, "Bad Water" and "Photon Bullet" -- but for a hard-SF fan like me, it was refreshing, because it was one of the only SFTV shows ever that really tried for scientific plausibility and intelligent futurism, at least until late in the season when they began bringing in more fanciful concepts like psi powers and aliens. What frustrated me was that the producers of the show kept saying in interviews, "SeaQuest isn't science fiction, it's a plausible extrapolation of the future development of real science." That's literally the definition of "science fiction"! That's the whole reason the word "science" is in there!!! But the general public had been conditioned for so long to think that SF was fanciful, ludicrous stuff like Lost in Space and Star Wars that they didn't realize that. So when they brought in new producers for SeaQuest season 2, they said "Okay, this year we're going to start doing science fiction stories," and instead they abandoned the hard-SF sensibilities of season 1 and started doing utterly stupid, ludicrous fantasy stuff and turning it into basically a remake of Voyage to the Bottom of the Sea. Which was really insulting to me as an SF fan and aspiring writer, that they believed SF was something so idiotic.
As for season 3, I barely even watched it. What I saw wasn't quite as dumb as season 2, but it was just too great a departure to interest me.