It is infinitely soloable. I'm not sure I'll play into the paid phase, but if I do it's because you really can just jump in, warp out and start shwacking stuff in minutes without whining for a group for 45 minutes.
Boring, sure, but if that floats your $15 a month boat it certainly can be done. Not bad for folks with real lives who can't afford to waste precious gaming time.
That is the best and worst thing about this game. Though I am in a Fleet, I certainly don't need to be. There is nothing in this game you cannot to alone or in a forced group all the way from ensign to admiral...
I actually bought the lifetime membership so I could just come and go as I pleased. I don't actually see this game as offering enough content to keep me busy for two years..