I'll agree the performances generally out-weighed the writing. I've always thought Janet was prettier than Chrissy, too, especially by Season 4 when her hair was cut shorter.
The plots were pretty paper thin, so yes you did have to care for the characters for the show itself to keep your interest.
Jenilee Harrison was apparently ABC's attempt to duplicate their success with Suzanne Somers. Evidently, some of the scripts that had already been written before Harrison was hired were still used, but with "Chrissy" crossed out and "Cindy" penned in. This is why the two Snow cousins had similar personalities; the writers wanted the same ditsy blonde role and Cindy was a simplistic filler. Also, some of Chrissy's gags were slated over to Mr. Furley (Don Knotts).
Yes, it is quite apparent from the episodes. Cindy did somehow seem "smarter" than Chrissy, to say the least. Her klutzy demeanor did setup many a physical comedy bit. I recall Jenilee Harrison saying in an interview that she and John Ritter would wear pads under their clothes to prevent any possible injury from their stunts. Chrissy did become more and more dingy and simply dumb as her tenure lingered on. In her last few appearances, she was perhaps at her worst. In saying all that, however, ABC seemed quite aware that Suzanne Somers was one of their biggest drawing cards. Supposedly, they tried their best to keep her around; they kept her on to do the "tags" at the end and kept her in the opening credits. With this, one is generally led to believe that the producers hoped everything would work out with Somers, that she would come back, and Harrison would be quickly written out. As we know, none of this happened, Somers was gone, Harrison was back-burnered, and Priscilla Barnes came on.
Season 4 did offer a shift for the show in general, especially concerning Chrissy. The Ropers were missed, but I personally loved Mr. Furley, and in some instances, I'm sure I preferred him over those prior.
I haven't read anything about Ritter defending them, either. DeWitt was hurt considerably by the treatment, and reasonably so. She had been one of the show's mainstays. Barnes, however, wasn't as upset. She apparently had wanted off the show shortly after her arrival, but her three-year deal rendered her enable to exit. As the story goes, Don Knotts and Richard Kline were offered recurring roles on the spin-off, but both declined. (I think Kline showed up once or twice, though.)
I didn't know about the pre-Somers exit problems, but that certainly makes sense. I'm sure there were worries about the Ropers being spun off, and how the new landlord would suffice. (Keeping in mind they weren't sure of the replacement at the time.) Norman Fell had a deal with ABC that if the spin-off didn't last more than a single season, he could return to the parents series. As the story has it, the network deliberately had the show run a season-and-a-half so Fell and Audra Lindley wouldn't be able to return to the apartment building. By the time the spin-off tanked, Don Knotts had successfully filled the shoes vacated by Fell and Lindley, and more cheaply I would imagine. (For the price of one I'd say.) Fell was upset about the treatment, but he and Lindley did one guest shot in Season 5 after Somers was already replaced by Jenilee Harrison.
