I just went along with the cast changes on Sliders, but as the stories got more bizarre and more like movie parodies, I eventually stopped watching. Maybe if it was the original cast I might've stuck with it.
The problem there wasn't the cast, it was the writers. What you're describing is the third and final FOX season. After Tracy Torme finally severed all ties with the show, the writing for the back half of season 3 was in the hands of morons who didn't have a clue what science fiction was, so they just ripped off old plots from sci-fi, fantasy, and horror movies willy-nilly. But again, that ended once the series moved to SciFi for its final two seasons and was supervised by a staff of people who were actually capable writers who understood a thing or two about science fiction and characterization. Even though the cast continued to change, the storytelling was still orders of magnitude better than the last half-season on FOX.
While The Dead Zone was amazing for the first two seasons and just very good in the third, it started to go downhill fast in season 4. The final crushing blow came in the sixth and final season, with the complete removal of or lack of regular appearances by Martin Donovan, John L. Adams, David Ogden Stiers and Chris Bruno.
Actually I liked that season better than the two that preceded it. Again, keeping the original cast doesn't count for much if they're in the hands of inept writer-producers, as TDZ was in its 4th-5th seasons. In S6, they had to drop cast members and relocate to Toronto to save money, but they were also finally able to bring aboard the showrunner they'd wanted but failed to get two years before. They abandoned the lame storylines their predecessors had imposed on the show, moved away from the episodic "Johnny Smith, Psychic Detective" stories and back to a season-long arc, turned Greg Stillson back from a second banana to a more central and complex figure, and most importantly, returned Sarah to a central role after two seasons in which she'd been reduced to a bit player. And the departed regulars did make occasional guest appearances throughout the season.
Wopat and Schneider wanted more money, but the Suits were convinced that the General Lee was the star of the show so, Wopat and Schneider basically went on strike and walked. Once rating plummeted, guess who came back to bigger paychecks?
Yes, I'm aware of all that, and I wasn't disputing that, so I don't see why you're pointing it out. I was simply saying that the temporary replacement of Wopat and Schneider doesn't meet the definition of the word "catastrophic," which implies something disastrous and permanently damaging, if not fatal. The Coy/Vance period, as lame as it was, was a brief and quickly forgotten interlude, and the series continued for two more seasons after it ended. Hardly a catastrophe.
By the way,
John Picard, did you know the executive producer of
The Dukes of Hazzard was named Paul R. Picard?