I'd say it depends really. If you just want to "clean up" the game and add a bit more content I'd say stick to the current engine, but if you really want to expand things move to another engine.
The main concern would be the 3D models you'd need, and also how much work would need to be done to port things over... but honestly RPGMaker stuff for the creature collecting is pretty jank and I imagine hard to set up. So if you want to invest a considerable amount of time into the game/concept the swap over might not cost that much time percentage wise.