I like science fiction (can you tell?). There are certain things you have to deal with when consuming SF, like the suspension of your disbelief. SF usually includes the use of technology that just isn't possible or physical phenomena never seen before. SF authors typically try to present these things in a plausible way, for example, building new tech off existing tech, or cutting edge scientific theorys. Further, there is a rule in SF that states that completely unbelievable tech or phenomena should be restricted to one or two occurences, and only where important to the plot or story.
Space:1999 is chock full of completely unbelievable bullshit.
In the first episode, there is an explosion on the moon which produces 10g of thrust for about 10 seconds, and pushes the moon out of it's orbit and into outer space. It's complete bullshit. Not only would such an explosion simply destroy the moon, it probably wouldn't move it from it's orbit, let alone flying off into outer space. But, since the plot of Space:1999 is completely dependent on this event, it can be overlooked.
But then in subsequent episodes, the moon travels to different solar systems, and as far as I can tell, at least a new solar system every two or three episodes, where a new planet (with aliens) provides a new episode plot. That moon sure is travelling fast to get to these new solar systems. Bullshit! and when it is there, it seems to moving at normal local planetary speed. Bullshit!
Then there's the episode where an alien race gives the moon an atmosphere by releasing gas from cannisters. Yeh, that'll work. NOT. And then it rains on the moon, in this atmosphere because the aliens generate a lightning strike. Um, where the hell did all the water come from?
And then there's the black hole (black sun) episode where some anti-gravity shield protects them as they fall into the black hole, and then some mystic star intelligence transports them to the other side of the universe. Just stop.
I've only watched maybe ten episodes, and I'm not watching any more. Blake's 7 is of a similar era, and is much more engaging.
To end on a good note, the sets of Space:1999 are incredible for 1974, and the theme track is a brilliant funky 70s tune.