^Having never tried a Kydex holster of any sort, I'm having trouble imagining a rigid shell pressed tight against one's waist as ever being comfortable.
You are correct that some kydex IWB holsters are not extremely comfortable IF the kydex shell is right up against your body. It does depend on whether you have an undershirt between you and the kydex. It also depends on your body type and where you carry it on your waist. If you are and out of your car a lot and you have kydex pressing into your spine, not comfy
The "Hybrid" holsters that mount the kydex onto leather or neoprene or other materials are hybrids The best of both worlds because you have the structure, safety, and retention of kydex (and cool custom patterns) and the comfort of a softer material spread over a larger area against your body.