I played about 15 hours of SPG before I realized it was very repetitive, shallow game play. A big fleet battle you have an hour or two into the game plays exactly the same as one 15 hours in. The ships don't really feel any different as they get bigger, your guns will do 2x as much damage but the enemies will have 2x as many HP. It's a zero sum game that only appears to change at a superficial level, it's a green slime, blue slime, red slime treadmill.
But maybe this expansion fixes all that, or maybe there's something really fun about SPG that I missed (they do keep making them so people must like it).