I mean, https://www.ranker.com/list/best-1960s-cult-tv-series/ranker... lists Smothers Brothers as a cult show.
To be fair, Smothers Brothers is not listed at https://en.wikipedia.org/wiki/List_of_cult_television_shows while Deadwood is.
On the other hand, that Wikipedia list includes Miami Vice (ranked #9 in 1985-1986 https://en.wikipedia.org/wiki/Top-rated_United_States_televi... ), The Golden Girls ("ranked among the Nielsen ratings' top ten for six of its seven seasons" https://en.wikipedia.org/wiki/The_Golden_Girls ), and X-Files (ranked #11 in 1997-1998, https://en.wikipedia.org/wiki/Top-rated_United_States_televi... ).
And X-Files regularly shows up on lists of cult shows, like TV Guide's at https://www.tvguide.com/news/reacher-season-2-release-date-c... .