Back then in the late 60s early 70s, the best television FX were probably on Trek and, oddly enough, over in the UK for Gerry Anderson's super puppet shows. In fact, the man in charge for the latter was Derek Meddings who did amazing work later on the James Bond films and for Richard Donner's Superman films.
Indeed. Anderson's FX were remarkably good. Space: 1999 had amazing miniature work supervised by Brian Johnson, and really good production values. Like Filmation's Space Academy a few years later, it relied on wire work and in-camera latent image compositing (i.e. multiple exposures/split screens) rather than traveling mattes, so the path that a ship was following was generally devoid of stars in the background; but it meant that every image was first-generation, with none of the degradation you got from matte work. And they had so many miniatures! Sure, they recycled a few alien ships as other alien ships, and reused stock footage of Eagles a lot, but they had more different ship miniatures in half a season than TOS had in its entire run. (Although some of those miniatures were part-Enterprise. There was a notable one, looking a lot like the Discovery from 2001, whose radar dish was the underside of the top of an AMT Enterprise saucer.)
By the mid to late 70s all the best FX workers were either scooped up by George Lucas and the fledgling ILM shop or were learning at Roger Corman's so to eventually get scooped up at ILM. Sad to say but the few sci-fi/almost sci-fi shows on television had pretty horrible FX apart from Battlestar Galactica but it was apparent even then they had a shortage of time and craftsmen and coped by reusing shots as often as possible.
Actually Space Academy benefitted from being put into production just after Star Wars wrapped and the first incarnation of ILM broke up, so Filmation was able to snap up a few of its FX artists and designers and produce some really impressive visuals for Saturday morning TV. And in the spinoff Jason of Star Command, they had some really good stop-motion creature animation, as well as "upgrading" the effects to motion-control bluescreen work (which was more flexible than the in-camera effects from SA but had obvious matte lines that made it look worse in some ways).