The only "riddle" part of that dungeon is that you have to go back and interact with a previous button for a second time. Since the buttons and crystals are marked with colors to show which are connected, it didn't seem like an area that would cause issues to people in my eyes. But I know that some players like to overthink it, and expect more complex solutions.
I intentionally created the riddle key item rather than adding something like those switches you suggested. Since the item is limited in quantity, it gives the players a reason to at least try the riddles, with a "cheat" to solve it if they get stuck and frustrated.
I did make the item usable for all difficult riddles, but the event with Kurohime didn't seem like it would require such a system to me. It's not one of the riddles where people complained about the difficulty before.
Sorry for your frustration.