I agree to some point - after all it's all about our personal priorities. Some players have Hagias maxed out at lvl 70 for example. Surely a Hagia at lvl 70 is better than a SoK as per fps/tile but still not many people focus on leveling it. I personally wouldn't invest thousands of fps to build something which gives me a chance to double collect my palaces, which i only have 4 of.
Which is the other problem with this GB - it's only good if you have like 10 Palaces/TFs at least. And you can't diamond collect. And you can get plundered. Too many requirements for something which is supposed to be a "Great" Building.
Oh and about Zeus/CoA - that's a very different story
Attack boost is the most wanted bonus in OF atm (like Nodge stated), so honestly I think if the Blue Galaxy was 10x10 and gave a/d like Zeus, more players would build it than those who will now