I have the X-T10 since summer and I absolutely love it, Raf photos editing is a pure pleasure with Capture 1 (Windows 10) the results fantastic compared to my ex-D90, but every-time I give a chance for jpeg and whatever the settings I use, the results are not much better than let's say a smartphone like the HTC 10, it's either over-sharpened or it lacks sharpening, or details are killed by the jpeg compression...
There is a huge universe between the jpeg out of the camera and the Raf, I think X-Trans cameras are made for Raf only if we want professional results and not instagram quality.
Your "criticism" is way over the top. And you're stating the obvious, to some extent.
There is a huge difference in the information content of raw data compared to a final image in JPEG format. You yourself may know the exact intent, how your image should look like in the end and how large it will be printed, but the camera doesn't know, and most of the time, users don't know upfront either what they are going to do with an image in the end. So how can you expect the camera to know exactly which information from the raw data to carry through to the final JPEG, which portion of the captured dynamic range to compress just right, how to use the proper amount of noise reduction and sharpening, etc?
The camera only provides a handful of processing parameters, each with a handful of possible values to choose from. Do you expect to get the same kind of control over the processing as from a full-fledged external processor?
Your are expecting too much from the in-camera JPEG engine, then you get disappointed and start a thread like this arguing against the engine, when you should really adjust your expectations. IMHO, anyway.