The 6D sensor is fine...its just exactly what you said, years behind pretty much every other company. Its closer to matching a m4/3 sensor than what Sony is producing.
If I'm shooting outdoors, in shifting clouds, I might miss an exposure by a bit. Or on a bright day against an open background, the camera might miss the exposure some. Being able to shoot to save the higlights and push the shadows gives me a lot of room. And having the flexibility to work longer windows at sunrise/sunset without bracketing...especially on days without a lot of clouds. All scenarios where Sony saves me a lot of time post-processing. That's less time I spend in my hotel room processing and more time I have to explore the city I'm in.
Though Im far more annoyed with the battery life decision and the weird video crippling than I am with keeping the 6DII sensor
As fair as 'real-life' image quality is concerned, I really don't think the 6D is years behind (the improvements in recent years have slowed down considerably), and certainly ahead of any crop sensor camera for almost all uses (of course if DR is the most important thing, there are alternatives). Just because it is not up-to-date as a hybrid camera, it is still an excellent stills camera (could very well be the best in terms of cost vs IQ).
I don't think missing exposure is a big problem if the result is already previewed in the EVF and easily correctable.
That being said, the 6D Mark II metering - improved from the 6D - seems to do a fine job as well, so I think the WYSIWYG is a little overrated.
As for saving time in post processing - I spend much less time with Canon images, because of the color being better.
I do agree about the RP battery being the biggest bugbear (for them, it was quite simple, lower price = more raised eyebrows and more sales)