Having rented an EOS R for a week, I can safely say it does nothing to assuage my impression that mirrorless cameras suck. Maybe in 5 years that opinion will change, but there is nothing compelling about then for me. I used a friend's Sony a7r III and had the same opinion. The feeling I have shooting with these is one of being removed from the scene. I feel like I'm (rightfully so) watching a TV show where there is a slight broadcast delay. Mirrorless cameras are not fast acting. There is a blur in the view finder -- the Sony a9 included. No refresh rate compares with the Mark I human eyeball. I have been a CPS Member since 1982. I am not technologically adverse. I started using Photoshop in 1992. I converted entirely to a digital workflow for work in 2001. I'm a proponent of technology. I do not see where this advances my style of shooting or workflow. I voiced as much at CPS at Photo Expo. I'm sad to see Canon jump so strongly onto the mirrorless band wagon. But I guess we can thank all those who shoot with iPhones for this direction since they all are used to looking through an LCD.
I agree with you in that I'm not crazy about EVFs. But unfortunately, preserving the OVF is pretty limiting in terms of what a camera could theoretically be capable of. Face and eye recognition will only get better in the future. I'm sure that cameras in the future will begin to back in more and more advanced artificial intelligence features as well. They will probably be able to do things we haven't even thought of a camera being able to do. But all of that relies on the camera being able to see through the lens at all times, making an OVF not really possible.
In addition, once camera manufacturers figure out how to make a high resolution sensor with instantaneous readout, we'll be at the point of having a camera with absolutely no moving parts. No shutter, no mirror, nothing. This will do wonders for reliability. Concern over having a shutter failure will be a thing of the past. Not to mention having nothing in the camera moving makes its ability to have a high framerate pretty much unlimited, as long as the sensor readout and processor can keep up.
Last, I've seen my EOS R focus on things in low light that I know for a fact that my 5D4 never would have been able to. At a certain point you have to face the fact that having a separate sensor for autofocus from the sensor actually taking the photo has always been kind of a cheesy solution. By getting the mirror out of the way, you allow all of the light coming through the lens to go directly to the sensor, which is also handing autofocus, allowing it to focus in much darker conditions than a DSLR could, because half the light was getting diverted up into the viewfinder.
I'm completely with you in that even the very best EVFs still don't feel right to me. There's still a little disconnect. But in a couple months of using the EOS R, I've gotten mroe and more used to it. I'll miss having an OVF, but I can't deny the fact that keeping an OVF stands in the way of a lot of new technology and better performance that will be coming to mirrorless cameras as time goes on.