Sure, the basic premise of Space:1999 has what I could charitably call 'dodgy' science (and perhaps more accurately term as 'completely unrelated to anything remotely resembling science'), and any sense of how exactly the Moon is moving through space - apparently shooting off at FTL speeds through the cosmos, slowing down to orbit around a star before whipping off again - does not have even the most slender connection to science.
...but it was still a sort of cool premise.
What?
You get to have your base on the moon series and your flying through space series. Take that cake and eat it, Gerry Anderson, you've earned it.
Well it's made very clear in the first season that it's all going according to some kind of cosmic level plan and that some kind of "cosmic intelligence" is behind it all.
Which I had totally not caught on to, or had forgotten when I watched it as a kid, but was surprised at when I watched them as an adult. So part of the show where you would say "But realistically...." just insert vast cosmic intelligence to explain it away. At least I do, and it works surprisingly well.
Is it still a bit dodgy? Sure. But IIRC nuBSG had a similar "God did it" or "Part of something larger than your ability to understand" vibe (not to mention 3 or at least 2 planet Earths that looked exactly alike). I think I can cut Space:1999 a little slack in that department.
Plus the model work, alien worlds and sense of space being really vast and mysterious were all very well done. Those aspects of the show made a bigger impact on me than Trek's.