You can, but then admittedly the EOS R is a beta test. The lack of dual cards alone is a no no to many including me. The rumored RS for next year will hopefully tick all the boxes.
As canon themselves put it - it is all about RF lenses in the new system. Sharper, more features, steeper price and all the rest. The pair of f/1.2s and that 28-70mm f/2 look incredible compared with anything sold by them before.
Agree about the lenses, but they do cost!! The are a few things I don't like about the rf lenses... 1. the control ring is at the front of the rf lenses, not a great place for me, the control ring adapter for the ef lenses put it at the back of the lens (where the aperture ring used to be) which feels right! and 2. the variable nd filter ef adapter can't be used with rf lenses, so 1 filter adapter for any ef lens, great when travelling and have to think about each component of kit.
I have a few ef 'L' lenses that work so well on the R, the extra features that the mirrorless system brings is to me a game changer, I find it hard to go back to dslr now the R has bedded in. Looking forward to the 'pro' version but have been happy to take this first step without regret. Even though canon say it is about the rf lenses, I would argue that the R body has some huge benefits.