The singleplayer experience, called Squadron 42, is not yet available. Online only for the public alpha test.
As to whether or not it's worth it, you can be the judge. They have multiple free-fly events each year (although the most recent one just passed I think) where you can download the game and play for a whole week for free to see if it's for you. I would wait for the next one to come up and try it then, if you are curious about it.
Generally, I try to steer people away from it even though I'm a fan of the game myself because it's just so rough around the edges and the initial mystique and wonder of exploring a vast solar system quickly wears off and gets replaced by tedium and lost progress due to bugs and glitches, so it doesn't make for the most enjoyable experience. YMMV.
I'd say just wait for SQ42 to come out, however long that may take. Possibly within the next few years if we're being optimistic.
I don't think it's possible to play the current game single player (offline) meaningfully. But there are very regular free fly events, I think you barely just missed one. I'm not sure I'd really describe it as worth it regardless for most people right now, it's still very alpha and has a very steep learning curve to actually work out how to progress on your own. But it is a beautiful thing to explore still.