I bet R6 is going to be very popular and successful. While R5 does have an eye grabbing spec sheet, it won't be in most people's pockets. R5 is brilliant, yet it generates 5DS-size files at the speed no slower than any 1DX, and pride with 8K video. But few have a workflow to handle that kind of throughput. To really make a R5 shine requires the investment of an array of high end gears: big "L" RF lens, large CF express, beefy computer for post processing, large storage, etc.. Without an ecosystem to support, R5 is either a waste of money, or a risk that hinders production efficiency.
For those with the budget, R5 sounds like the dream, but for average folks and many of the enthusiasts, R6 fits the bill much better.
R6 is practical. It isn't trying to win spec sheet credibility. It just focuses on doing what the majority needs, and manage those tasks really well. For video, it looks quite capable for HD and 4K. R6 might be a baby C500 mark II - if Canon shows mercy with its cripple hammer - and that's incredible. For stills, it seems like a 1DX mark III in Live View mode, which is superb. I am quite happy with the 20MP, which, though not big, hasn't been a problem for Canon's classics like 5D mark II, mark III, and the 6D. It's still much more than an iphoone 11 and DR and high ISO performances "should" be strong. Plus the smaller file size allows more flexible flow in post production. You don't need to build an ecosystem for this body, just put on an EF/RF lens and R6 will give you incredible results.