I’m probably just echoing what others have said here, but in my eyes Mannequins modules hit the sweet spot from a design perspective: immediate interface, relatively simple concepts, and vast possibilities in use. They all offer a lot of functionality, but there’s an ever present degree of limitation due to the interconnected nature. I personally find these limitations and interconnections extremely inspiring and conducive to experimentation and exploration when patching them all together.
For example, the other night I was patching Just Friends (sound mode) into Three Sisters and accidentally found a fairly convincing steel drum sound. I wasn’t trying to make a steel drum sound, prior to then I had no idea what elements I would put together to make a convincing steel drum sound, but due to the simplicity of the interface I was able to deconstruct what I had done very easily. That mixture of learning synthesis and sonic gratification is something I feel very often when I patch with these modules.