This is exactly how I felt 2 years ago. I was ready to never pick up a 35mm camera again. Then I bought a primitive Zeiss 6x6 of a pre-WWII design, ditched color, and started estimating the focus distance, using sunny 16, etc. Now I love it more than ever and my photography has really improved. You don't necessarily have to step way back to the stone age like I did. The point is, maybe you just need a change. Do something crazy and shoot a completely different format, film and subject matter for a while.
Your mention of a raising of your standards is very perceptive. I do know from 35 years of martial arts that this feeling often pre-sages a breakthrough. It doesn't mean you really are worse, only that you've grown enough to perceive your faults. That is a necessary, but not sufficient condition for improvement.
But like you say, go not to the elves...