The rune thing is so frustrating and painful, in a really needlessly-problematic way. It takes forever to get it to even show up (for unexplained reasons), then it just randomly will never give you the main three (merge, unmerge, reversion) for months at a time (for unexplained reasons).
Then when you finally DO have them they just don't work at all, for unexplained reasons. Each tedious step of this loop only barely has a chance to trigger and if something goes wrong you have to wait an eternity for another roll of the unexplained mystery dice roll. Sometimes both unmerge and merge just silently break and never move the transformation with no explanation.
All of this could maybe be forgiven as working that way on purpose if the directions it keeps railroading the story into weren't immediately a repetitive loop of the same content that runs dry way too quickly. Chapter 2 is next to impossible to unlock properly because of all this poorly-timed railroading and random silent failures. The whole allure of a permanent ending quickly gets hollow when there's nothing to do when you get there.
Even the skip to chapter 2 button doesn't work right because it sends you to a broken state where no runes are unlocked so the game keeps tripping over itself trying to do chapter 1 content out of sequence in chapter 2.
I want to get into the story but my immersion keeps getting broken hard with the railroading and random failures ruining the mood.