EOS R 'less professional' than EOS 5Mk4 ?

Forgive me if this has already been said on this thread, but, nonetheless, here it is; a pro camera is any camera that a pro uses to make his work product. Without exaggeration, I feel quite confident that I could use either my iPhone or a low level Rebel to create professional content that most clients would happily pay me for. Yes, it would be harder to produce pro work with those, rather than with my EOS R or 5D4, but it would clearly be possible.

For an example, here is a shot I did recently with my iPhone X, when I passed by a window near where I had sat down my pistol, which I had just finished cleaning.

The idea of pro still cameras has been quite ill defined since the days of my old Nikon F3’s. Back then, pro cameras were a little more easily defined by their very large range of accessories, like fast motor drives, interchangeable finders and focusing screens, Polaroid backs (yes, I had a couple), extended film backs, more external controls, finer adjustments, larger and more accurate viewfinder images, greater precision, environmental protection, longevity and ruggedness. Some of these things still do define today’s cameras that are labeled as pro, but there are now so many mid-level models that can do the same jobs (except for frame rate) with maybe a pinch less ease, that calling any camera “pro” is no longer as relevant as it once was.

As between an EOS R and 5D4, it would be foolish to call one or the other more "professional." If you become proficient with either camera, you can easily make pro grade work output, and although they both have their comparative strengths and weaknesses, they both are fantastic picture making tools. In the end, that's all that counts.