One of the things with Unmortal that I have been less than happy about, but which I will most likely just choke down and move on with, is the way the world in the story functions in a certain way. This makes me uneasy for the same reason I'm not fond of fantasy settings with overly elaborate magical systems. I think they are distracting and needlessly complex, and a sign that the author's interests are not really with the story but with the world the story is set in.
But I have to balance that against leaving the reader feeling there are no rules, that anything can happen and therefore nothing makes any difference. It's just that once you set up one rule, five more emerge from that naturally, and so you have to keep the number of actual rules to a bare minimum lest you end up writing a rule book. I feel like there may be too much unexplored incidental complexity for my own good, but if I yank it out, then the story is even less functional on its own terms.
One of the commenters in Goodreads whose reviews I respect once theorized that an overly complex magic system in a fantasy story is a sign of insecurity on the author's part. They don't trust the story or the characters to behave as intended and deliver the drama, so they offload that onto the setting. Small wonder such stories always feel like the characters and the story itself come in a distant fourth, way behind the convoluted magic system and the tiresome history of the world and the maps in the endpapers. This isn't to say maps in the endpapers or any of that other stuff are bad, just that they can't carry the story if all the actual heavy lifting has been offloaded to them.
If people feel they trust a story to be straight with them, in the sense of emotionally honest and playing fair with the reader's sensibilities and sympathies, you can get away with a lot. But that's really hard to do. So much so that I can see why folks would rather just try to make their story more akin to a pocket watch, with all the gears meshing perfectly (if boringly), than to make it more like a toy of sentimental value.
I've more or less resigned myself to the idea that it's too late to rework the story in any significant way. If Unmortal doesn't work because there's too much engineering in the setting, then all I can really do is roll that understanding forward into another project. It has to stand or fall as I've put it together, and if it falls for some, then maybe that's just because not everyone likes everything.
I'm facing an analogue of this issue for my next project, Shunga-Satori, which is driven by dream logic and the unconscious. It runs even more of a risk of feeling like a story where everything is possible so therefore nothing makes any difference. Wish me luck.