A few things bothered me with my former 5Ds, and made me switch to the 5DIV.
First, I missed having in camera GPS, like the 6D I had before the 5Ds. To some degree I also missed having wifi.
Second, I did not appreciate the high resolution. It made many (most of) my lenses look poorer than they did before, because what’s the point of high resolution if it looks worse when zooming in to details? (Yes, you do get more detail, but the 100% quality gets poorer). Further, I found it annoying to work with the larger files. It slowed down my computer too much for me to have a decent flow when editing, for not to speak of when I scrolled through images for selecting the keepers.
I did also always shoot at faster shutter speeds than before, making it relatively bad for low light use.
Last, not having dual pixel AF in live view makes it much less versatile than the 5DIV.
At this point in time, I think 30 megapixels is a sweet spot for a FF sensor. Hopefully RF glass and IBIS will make me embrace the R5...