The entire point is that there's nothing particularly unique about it. It's essentially just another Space Mountain and is not employing any technology that hasn't been seen much earlier. Gringotts doesn't utilize as much motion, but it doesn't mean it's not capable of it either. I've had a few rides where it bugged out and the vehicle spun in two or three circles. The issue is that people are always claiming that a merit of Guardians is that it's unique and it's very clearly not. Vekoma's technology is incredibly similar to what Intamin had already innovated.
I got to ride it 11 times during my recent 10-day holiday and I got to know its layout fairly well. You are right in that projections, controlled turning of the vehicle, and indoor coasters have been done before, but this is actually incredibly well designed and I think better than any other inddor coaster I've experienced. I thought the same about Paris' Space Mountain. When you get to know the layout it's easier to appreciate the thought and design that went into the layout, to give certrain forces and feelings at various points.
The theming? Meh. The "story" doesn't add anything to the ride, I don't think I followed much of it anwyay. Screens and projections and pop songs do not a good ride make. It would work just as well, if not better, if it was just a ride about the Big Bang and your journey through the newly created universe, with an appropriate atmospheric soundtrack.
Highlights:
The one complete 360degree rotation about halfway through the ride.
The upwards launch towards the end (although the effect diminishes somewhat the further back you sit)
The helix around the moon. OMG that is so well done. It gets tighter towards the end and drops at the same time, while you're sat at an angle, giving you a lot of "oomph", especially towards the back.
It's not "essentially just another Space Mountain" at all. But even Space Mountain wasn't just thrown together. Those drops occur in very strategic places and with a specific profile to give maximum impact.
Technology is just a tool that can be used to, erm, tell a story. It can be used well, or not, and it can be used to enhance. Doesn't really matter if Vekoma did something similar to Intamin, I would argue that this ride does it better than Gringott's.
[Edit: I get that you were responding to the "unique" argument, that the technology it uses is not unique and it's been used before. But my point is that it's being used in a better way, and it does provide a unique experience, considering the track layout and how the rotations work in harmony to provide certain forces, not just to point you to a particular object)