When I started with the Pentax 6x7, it was after having used a Mamiya RZ67 for a year, so the frame size and aspect ratio was something I was used to. But I was using only the waist level finder with the Mamiya, and of course the prism finder for the Pentax. I think this has had an influence on the photographs of people, because of the way of interacting with the subject, the height of the camera etc. So far I enjoy the Pentax, though, for field work and hikes. If you have had the camera for a long time, and the decline in results is something that has happened suddenly, then I think you have to think about whether there is something else distracting you. Maybe work, family or social life. Maybe you are a bit depressed and you do not realise it. That will definitely influence the way in which you look at your photographs. But I am not a psychologist, just noting that you sound a bit strung. What helps for me at times, is to stop all forms of photography and photographic reading / learning, for a couple of weeks. Stay away from all the forums you frequent, stash your photo gear away, close the books and put them into the book shelf. Then go around, and LOOK at the world without photographing it. Ask yourself what things you like in the world around you, what you find interesting, what reflects what you are aware of in yourself. Simply be aware of your world and your response to it. Then after two or three weeks, go and photograph those things that moved you.
I find that when I photograph my children in a non-intrusive sort of way, it almost always breaks the ice for me. It is not that the photos are necessarily great, but the fact that I enjoy seeing the results none the less, makes the effort worthwhile. Eventually, when I get the opportunity to photograph other things, I have a positive mindset. I should also add that I seldom shoot CN film on my Pentax. My BW results tend to please me slightly more on average than the colour negatives. Maybe it is because it is sometimes really difficult to get the colour to gel with all the other elements in an image, while BW is forgiving in that sense.
As a last thought, the only sure way to get no images worth keeping, is to take no images at all. The only way to increase your hit rate, is to practice. The latter must have an element of evaluation / critique and then repeating the effort with the added insight. Just continuing to randomly shoot things without closing the learning loop will probably not help you understand what is wrong with your photographs, which may more be a lack of visualising properly than faulty technique etc.