Thanks for your detailed reply! My biggest gripe with the game is also the bland-looking caves that look too similar from an outside perspective, I think it was me working with the map and really learning it inside and out over a few days that blinded me to how similar it all is. (oops)
The instant-end bug was a very simple issue, there is an integer to count how many crystals you have collected, this plays specific voice lines, and enables the end trigger. The problem came from me manually setting that integer to the max value for debugging the ending sequence in my haste to export the game... Which also disables most of the voice lines and plays the ending line at the start of the game along with enabling the ending trigger. The worst part for me is that is was a super easy fix once I discovered it, and I will update the submission to the fixed version after ratings close.
I am very happy to see your constructive feedback and I'll be sure to check out your game as well!