They keep getting better (EVF's), to me it is kinda like watching a very small TV, so I would rather look at an articulating screen/live view rather than the tiny EVF. Done well they can be quite good, some, not so much. I have both, although not "high end", I still prefer OVF. That could change someday. They are a bit of a battery hog, but that could easily be countered with a battery grip, or carrying an extra battery or two.
Based on your post, you haven’t seen a mirrorless camera in the last few years. Unless of course you mean a P&S camera.