I largely agree with your argumentation. What I like about the 5DsR is that extra 3D-pop it tends to render, especially when paired with good lenses like Zeiss primes. I also very much like that the anti-aliasing filter is cancelled out as I really don't miss it and it mostly just blurs out pictures.Wow...this thread spun into name calling fast...
For me, the megapixel race was over once I hit 20-ish full frame mp and that was a long time ago. A good photo is a good photo regardless of the quantity of pixels over that particular boundary. I have no desire for a 5DSR even though I take a lot of landscapes. In my humble and probably biased opinion...anything over 24mp is koolaid and pushed by camera marketers and people who photograph walls and lens charts. Give me a well rounded and super versatile camera like a 5Dmk4 any day over a 5Dsr or what ever the latest super high mega pixel bragging monster will be. It's a bit like the frame rate argument....I've never seen the need for 14 fps either and I've shot on many wildlife workshops. Anything over 5 fps is more than adequate if one times their shot. Only the "pray and spray" shooters seem to need more. I can't see many clients choosing images because of a greater system resolution vs a great photo.
On the other hand, the resolution of displays increases (Full HD --> 4K --> soon 8K... however pointless 8K is with regards to the limits of human vision and common viewing distances, but that's another story) and cropping also occurs dependent on the type of photography we do and the motives we capture. This is where resolution becomes dear to people, especially birders and wildlife photographers I imagine. However, the utility is largely about probability of needing it versus the costs of having it. I can nothing else than fully acknowledge that even my years old 5DsR is a very niche camera, and the 5DIV is simply better for all-round photography -- unless you often face the needs to crop in or print really huge.
EDIT: Similarly I see use of high fps for a few photographers who need that to capture the moment, the occurrence of which happens in times that fall beyond our human reflex times. I'm again thinking about bird and wildlife photographers, but also sports and such stuff where things happen very fast and spray-and-pray is the only way to reliably capture the best moments. One should keep in mind that those are all corner cases with regards to some sort of "virtual" average of photography needs.
That said, I believe there is a need for those niche features and performance levels. However, I see that all-round cameras and typical photographers will more likely be limited by baking these in just to make them look competitive on spec sheets because of all the ungrounded hype out there.