There's loads of great scifi/fantasy especially from British tv in the 60s/70s and 80s , but a lot of it was for kid's tv, presumably because writers couldn't get airspace for adult scifi programmes. So that we got great series like Children of the Stones, Into The Labyrinth, Chocky, The Tripods, Robin of Sherwood, Doctor Who, The Changes, Space 1999, Logans Run, Thunderbirds, Stingray etc etc.
There were still some great adult British 60s/70s scifi/fantasy like The Stone Tapes, Quatermass,, Blakes 7 but it was generally poorly represented which is probably why so many adults lapped up scifi that was primarily aimed at kids like Doctor Who.
In the case of the Tripod, I wish they had been able to complete that series.