My advice would be:
1) It's great/helpful that you have a whole complex universe/story fleshed out, but maybe choose one/a few compelling areas or events to focus on for now instead of doing the whole thing? Then you can get back to other areas you want to explore after you finish the first part if you want, as sequels or spinoffs or something?
2) Another idea is to do a super stripped down version that mostly features just major events and leaves out other stuff. It could feel rushed, but it would be easier to finish while staying engaging. Like just the scaffolding of a story basically (not necessarily less interesting though)
3) I feel like often, the exact details/logic/coherence of a story doesn't matter as much as the feelings or atmosphere it creates. So maybe you could leave out some explanations or worldbuilding info to prioritize interesting/impactful scenes or just the experience of being in your story's world (I feel like Ghibli films are a good example of this).
Anyways, those are just some initial thoughts I had. Good luck!