The optical viewfinder with focus parallax is the only professional option, bad for Sony despite its hideous mirrorless, very cheap but not professional.
I learned photography with a Contax II 1938, with that type of viewfinder and then I adored it with the Leica with automatic parallax corrector (a jewel of German optics), Nikon and Canon DSLR. Taking a camera to the face puts us in a more stable situation than the dimly lit electronic viewfinders. Now they promise AMOLED visors that are tactile, triple the brightness and consume much less current, but it does not solve to stretch the arms. I do not shoot with the distal phalanx of the index (fingertip) but with the distal interphalangeal joint, which makes the artifact movement is minimal. Take the test and you will notice the difference. With an electronic viewer that is not possible,
With the direct viewer we can have better control of the horizon line and the vertical ones. The electronic viewer does not remotely show the reality of the photograph or the video. It is a derivative of the universal use of smartphones, but just one of the weakest.
I can maintain more stability and see everything "as it is" and not "how it's going to come out" so I can control the "rabbits" that usually appear bombarding unique digital photos.
The best cameramen, directors and directors of cinematographic photography use the direct viewfinder in cameras like the Alexa, and the Red, and a piece so expensive and difficult to treat is not done in vain, if it were not better and safer.