The frustrating thing with the ending for me is that it suffers from a problem so common in science fiction that the Encyclopedia of Science Fiction has an entry for it - "sense of wonder." The sense of wonder is the thing that appeals to people about sci-fi when they're young, and it's what a lot of sci-fi writers spend their careers trying to replicate. It's an addictive sensation. The problem is that while trying to blow your mind with the revelation of some heretofore unguessed-at universal truth is an awesome idea for a story, it's hard to just invent transcendent universal truths out of thin air.
Some sci-fi writers cleverly cheat a sense of transcendence into their stories through a dirty trick called "conceptual breakthrough," which is a flavor of plot twist that involves the sudden, shocking realignment of the narrative's perspective, so the story you thought you were reading becomes something else entirely. That moment in Book of the New Sun
where the reader finally catches on that the castles and towers are actually old rotting spaceships is a good one - holy shit, this fantasy story is actually science fiction! The bit in ME1 where you find out Sovereign is actually a Reaper is a good example as well - suddenly, your sense of the entire plot and the stakes involved become completely realigned. Or there's an infamous last sentence in an otherwise not actually very good book called The Weapon Shops of Isher
by A.E. van Vogt where the story, which to this point has been a third-person narrative about a heroic human space badass (kind of a proto-Shepard), suddenly ends with the line "This much we know: This is the race which will rule the Sevagram." Bear in mind that that is the first time that word has appeared in the book. It blew a bunch of 1950s kids' heads wide open as they argued about what it could possibly mean: was the story being told to us by a third party within the story? What is the Sevagram? Has someone been watching the hero this whole time?
Basically, the vibe you're going for with conceptual breakthrough is this:
It's a good way to generate the sense of wonder, but it suffers from the usual caveats involving any plot twist - it has to be surprising but feel fair, it can't invalidate what has come before, and so on. There are plenty of bad examples of it, like some of the cheesier Twilight Zone twist endings.
Other writers try to achieve the sense of wonder by sheer scale, often by literally just throwing a big object like a Dyson Sphere or Alderson Disk
into the story. Which is cool, I like that crazy stuff as much as the next guy, but the sense of bigness and scale only works for so long, and often the actual stories
being told are incredibly prosaic and don't reinforce that sense of bigness at all. Often they involve heroic space marines fighting evil aliens for control of the object.
Other writers try to go for the sense of wonder obliquely, deploying powerful symbols and appealing to the emotions with hints and suggestions rather than actually delivering explanations that can't possibly satisfy. I like this approach a lot, and I think it's part of the reason Dan Simmons' book Hyperion
works so well - he used to be a horror writer, so he just sticks a bunch of vivid, memorable imagery in his sci-fi and leaves it to you to guess at the meaning rather than sitting down and going "well, robots and humans hate each other, and..."