Yes, you should obviously stay away from the EOS R!
Why would you want to be happy with your camera?
I shot a wedding with a guy who was using Nikon gear a couple weekends ago. He kept complaining how it would front focus on objects behind the subject. LOL.
DSLR's are already dead. The EOS R is one of the best AF cameras on the planet if not the best.
But by all means, buy a D850. It's only twice the price of an R with no tangible benefit.
No material object should determine one’s happiness. ;-)
The newest generation of Nikon cameras can be AFFT’ed on-site, in seconds. (Nikon AFFT = Canon AFMA.) Of course, regardless, I would rather adjust AF before the shoot. I have encountered somewhat more need to AFFT Nikon DSLRS, than Canon, but largely, my SLR lenses focus well on my SLR cameras. Notably, my most-serious experience with a Canon missing focus was with an EOS M3, and its 22mm EOS-M lens, so it is not true that mirror-less ILCs are immune to focusing problems.
The EOS R, and Nikon Z6/Z7, do, indeed have some technical AF advantages over DSLRs, but these advantages are not yet applicable to all shooting situations, so, I would rather wait, until a future generation of the R or Z, for shooting something like a social event, in challenging lighting conditions. (I may, however, try an EOS RP, soon, simply because I like its control set, better that the EOS R, and the price point is attractively low.)
I can buy an EOS R, today, for $1999.99 US, and a D850, at the same seller, which sells at MAP pricing, for $2799.99. The D850 does not cost twice as much. ;-)
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By accident of availability, I learned to use Canon and Nikon DSLRs at the same time. I love specific lenses made by both Canon and Nikon, too much to quit either system. Dabbling with Leica-M is fun, too. I am, certainly, not an expert.