I don't mind the sound as much as you do Dan. I rather like some of it, but I take your point.
The C15 reminded me that a lot of the precise synthesis and control we love, isn't really needed to get a musical idea across. Lovely synth of course, but not attractive to rock musicians, (give me a B3) pop musicians (can it keep up with a Kronos) or even a lot of jazz (can it sound like that 73 Suitcase Rhodes) players.
So what do have left? Experimental music. Cross-genre music. Pretty small marketplace. It's why Kurzweil killed the ribbon and Yamaha the breath controller, I think.