For the first 4 seasons the show was in the top 5, but in season 5 it dropped out of the top 30 and was cancelled. Did CBS move the series to different\bad time slot. Did the quality of the show significantly drop in season 5?
shareI don't know if the quality dropped, but Buffy and Jody probably weren't 'cute' anymore to most of the audience. They'd grown up (even though they were still supposed to be young kids.) The same thing happened to 'the Partridge Family.' Danny Partridge was not as funny as he was the first two years. Jay North in Dennis the Menace, Jerry Mathers in Leave it to Beaver...they, and other child stars commit the sin of 'growing up,' and sadly, their shows are canceled.
shareI recall that. It probably was a major reason for the show's dip in the ratings. Jody in particular--he was obviously maturing into an adolescent and the scriptwriters insisted on having him continue to act like a prepubescent little boy. It almost gave a slightly creepy impression that he was mentally defective in some way, with the combination of an adolescent's physique and a child's mind.
Buffy's was somewhat the same dilemma, but I think maybe because Anissa always seemed a bit grave and withdrawn on the show, even as a child, it was perhaps not as immediately noticeable with her as it was with Johnny Whitaker.
Kathy Garver has stated in the interviews on the DVD sets (Which I own thankfully), that the series was still viable and it wasn't a significant drop in the ratings. The year 1971, a new president took over CBS and purged all the bucolic rural series (Green Acres, Mayberry RFD, Hee Haw, ETC).
"Family Affair" wasn't bucolic but was considered "old fashioned" and with the new TV trend that year going to more sophisticated, more realistic fare ("All in the Family", Mary Tyler Moore", "Sanford and Son"), "Family Affair" was cancelled along with "My Three Sons".
Another reason was that by year 5 clearly Anissa Jones and Johnnie WHitaker were no longer cute and adorable. Anissa, particularly looked as if she just hated being there in many episodes during the last season.
So, what do the producers resort to when a series starts showing its age? A recourse that never works. Bringing in a new character: Emily, annoyingly played by Nancy Walker. That didn't help just like "Oliver" didn't help in "Brady Bunch", "Ricky" in "Partridge Family", "Dodie" on "My Three Sons" or James and Cassandra in "Little House". In the case of "Family Affair", bringing Nancy Walker on was the final nail in the coffin to coin a time worn cliche'.