One major mistake this show (which I loved) made...
...was abandoning the original set/locale that appeared in the two-part pilot.
The design of the place borrowed heavily from The Prisoner, but when I saw this as a kid I hadn't seen The Prisoner, so it was all new and exciting to me.
Ultra-modern cards, underground tunnels, weirdly generic foods, the idea of a race of androids--it was all quite compelling and fascinating.
The later episodes, when the family found themselves in very ordinary-looking settings, suffered by comparison. Only the episode focussing on Jonna Lee's character brought back some of the compelling surrealism of the two-part pilot.
It was a great, great, great pilot show, but the rest of the series suffered, and one of the main reasons was departing from the fascinating, surreal city where they began.