Thanks! I get 27 FPS during playback in animate mode with quite a beefy computer. Here's the Metrics view with your project:
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Clipping is normally expensive, especially when clipping many attachments, but hiding your clipping attachment improves things only slightly (1 FPS). Deleting all meshes, regions, and paths reduces vertex transforms down to 0 and then I'm hitting 44 FPS. That is still bad, so the vertex transforms are not the main problem. Deleting all constraints gives 47 FPS, still bad. How could that be when there are only bones and slots? Wait, why are all these slots hidden?! Reload the project, ctrl+H to show all hidden bones and slots:
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The project is about twice as large as it seemed at first! FPS is 19. Reducing vertex transforms from 130k down to 50k (by removing meshes) and the FPS is 60+, as it should be.
We will look into making Spine more efficient and I'll report our results here. From the quick look at your project above, I'd say you just have too many vertices. It's pretty unlikely you actually need so many vertices! If you are exporting images or video, then the number of vertices don't matter as long as Spine's performance is not a hindrance. If you are planning to use in this with a runtime, then I'd say your project is much too heavy and you almost certainly need to rework things to use as few bones and vertices as possible. Spine does a lot more work than the runtime needs to do, but with this many vertices I doubt performance on any mobile device would be acceptable.
I can say you did well by not using deform keys, which can use a lot of memory.
You might check out this part of the user guide about performance:
Metrics - Spine User Guide: Performance
