It's playable, just not interesting. All the pieces are there (although a few are not very well designed), but it lacks some fundamentals to make the whole interesting - mainly, the AI is just nowhere near competitive.
So right now, it's more like a technical demo than a real game, because you can do all the things you'd do in the real game (colonize, expand, design ships, research) but there really isn't that much motivation to do all this, as the AI's performance will not justify it. Why research and design platform-buster ships and weapons if the AI isn't using platforms? Why focus on heavy armors and shields if the AI will only crank out poorly equipped fleets?
Also, as mentioned above, balance is very questionable. Sure, it's impossible to perfectly balance everything is such a complex game, but a reasonable state of balance can usually be achieved anyway. There's no such thing in SotS 2.
Come back in 2-3 months, ask the same question. If things haven't improved in terms of AI and balance by then, just forget about this game - there will be other 4X with tactical combat in the future, and some of them might even be playable out of the box.