I was thinking that it might be very like Doctor Who in that regard. The early episodes were cheesy, but when you looked past all that, it got better the more you watched.
Every so often there is an episode that is very weak, its like they lost every other page of the script but most of the episodes are very very good. (Their fight scenes desperately needed a “fight coach”!)
From what I gather, they didn't have much money back in those days. They probably couldn't afford it at the time.
The sets are much much worse then Star Trek: TOS.
Even worse then the original Lost in Space.
Its clear as the series caught on, more investment was made in it.