Did I say there was something wrong with the 5DIV?? That's exactly the point that it's still the best. All Canon mirrorless cameras released after 5DIV have DR worse than 5DIV.
The difference between the 5D4 and R (0.1ev) is inconsequential. They have the same DR for all practical purposes outside a lab test.
DR has been "stuck" for everyone. The D800 set the bar in 2012. Very few cameras have matched or (barely) exceeded it. It would appear that DPAF is the reason why the 5D4 and R are roughly 1ev behind on this metric, as you can process a DP RAW file to match the DR of the D850. That said, 1ev (regular RAW file) is a tick or two on a NR slider. It's nothing like the D800 vs. the 5D3 where the D800 shadows would reveal details that simply weren't in the 5D3 file.
I suppose you could complain about the DR of the RP, but first you would have to find a FF camera at the same price point.
This is one of those areas where people act like "Canon is behind" with "sensors that are years old" without realizing that the industry as a whole has not moved forward in 7 years on the metric in question.
On a similar point: it seems like the video discussion is progressing as if Sony had 4k60p and Canon had no 4k. Last I checked Sony offered FF 4k30p (better high ISO) at 100 Mbps while Canon offered cropped 4k30p at 400 Mbps (far better for grading). That's not a clear win for Sony, and more than one review by a professional cinematographer points this out.
As I pointed out in another thread the stand out video MILC right now is not a Sony but a Fuji, the X-T3 with 4k60p at 200 Mbps, 4k30p at 400 Mbps, and that gorgeous Eterna profile which means you might not even need to grade the footage. And still the R makes sense if you have Canon glass and/or want to match the footage from a Canon cinema camera.
I won't be surprised if they dust 5DSr sensor, tweak it a bit and release a mirrorless high-res R version.
That sensor still ties for highest image quality in 35mm format 4 years after its release. With the right glass it can quite frankly give MF a run for its money. Mine has done nothing but impress me in all respects at all print sizes.
If Canon were to reuse that sensor they would still have one of the best high resolution systems on the planet. If they go with the rumored 75mp sensor it will put them that much further ahead.