So, I've been trying to get all the stamps and such and one thing bothered me: The mimic isn't very well designed, and by that I mean I do not feel incentivized to play its game most of the time. The idea of collecting gold at the risk of increasing its damage output is good on paper, but in practice it makes battling it a slog since it doesn't produce real gold often enough for it to get enough power from greed. Not to mention that I think it should never appear as the final boss because it makes the gold gimmick moot.
Glad to hear you're still playing! That's pretty true now that I think about it, I realize that I play against Mimic the same way. I'll have to rework it
As for it being a final boss, I currently plan for the full game to go endless so I have it to appear as a second boss in the demo just to get feedback on whether the boss scaling is balanced
Incidentally, I hope to push a patch early next week just to implement changes based on feedback I've gotten on the latest version before I get back into the content grind for the next full update. Your feedback about cash gained on battle results not showing the base number well is one of the changes, so keep an eye out!