It's just that to achieve this detail a lot of conditions have to be met at the same time, i.e. "studio work" or "controlled setting" or "tripod landscape". You cannot just snap away and expect 50mp to be sharp at pixel level - and if it isn't, there's really no point to go for this resolution in the first place.
Err, aren't lots of shots done in the studio, controlled settings or on a tripod? Especially professional work.
That's what it's for . . .
Well yeah, thats also Chuck makes the point about a more robust tripod mount, controlled shutter, delay timing and so on.
Nearly all my landscape shots are done on a Manfrotto 055 tripod, live view/mirror up, and remote shutter, manual focus, manual exposure (watching the histogram) with info on, and a bracket 1/3 - 2/3 each way. Then its on to extensive post with Capture One, then PS + NIK + Topaz, all in 10-bit/channel ProPhotoRGB color workflow. Yeah, time consuming - and I do stare at images for hours.
Now I did rent an A7R + Metabones for a couple weeks last year. Did side-by-sides with the 5DS. The A7R shots did have a different quality - more resolution of course, and a bit more contrasty - a different 'feel' or tone. As I work through sets, I am using some from the A7R and some from the 5D3. Yes, you heard me, sometimes I do prefer the 5D3 shot over the A7R.
I am still thinking about using an A7R as an alternate "camera back" on shoots. I'd love to consider it for primary work, but as I noted in another post, I dont think the EVF replaces an optical viewfinder (though it has some nice features like peaking and will get better); nor do I like the small size (big hands); or the layered menu system (reminds me of some Yaesu HAM radios where I have to bring the manual to remember the option numbers). But I may still get one. June is four months away and maybe Sony will surprise.
But for now, the 5DS R will take care of my #1 need - resolution for prints. I have the super computer, could use some 4K Eizo or NEC PA monitors now
Everything else is irrelevant to my shooting or can be handled in post.
Unless I decide to go crazy and get a 645Z.