Speaking just for myself, I've owned many DSLRs and the viewfinders on many of the APS-C modes have been abysmal, like looking at a dark window at the end of a tunnel. But the same can be said of the EVFs in many budget MILCs - often small, coarse, contrasty and generally unpleasant. I actually think that the "WYSIWYG" aspects of EVFs is overrated. For me, the real advantages of MILCs lie in the faster and more accurate AF and tracking systems.I'm not sure though there is a huge number of photographers who prefer a DSLR to a MILC per say. It probably depends on their experience with a MILC. A MILC has alot of advantages but the quality of the view finder is key. Newer ones are quite excellent. Silent shutter and seeing what the exposure actually is are huge advantages with MILC, maybe you have to use a DSLR to see what you are missing.
Currently I have a 5DMkiv and an R5. Although the R5 has many advantages over the DSLR (quieter, lighter, faster, better sensor, more precise AF etc), I still very much prefer the optical viewfinder on my 5DMkiv. I love the fact that the viewfinder works the same way as my own eyes - seeing light levels as they exist in reality. To me it's a bit like comparing the experience of looking through a window, to looking at a TV screen. I also love the way that an optical viewfinder is always "on" - I can raise the camera to my eye and it's instantly available, whereas with even the best MILCs there is a brief time lag before the EVF springs into life.
The truth is that each type of camera has a different "feel", and while most people nowadays seem to prefer an EVF, there are many who just feel much more comfortable with an optical viewfinder. It's also equally true that the viewfinder experience with either DSLR or MILC varies considerably according to how much you spend - Rebel viewfinders are pretty awful compared e.g. to those on a 5DMkiv or 1DXiii.