Question 1: What kind of areas of photography are yours?
Question 2: What type of actual EVF did you test or have in use to complain that much about?
I pretty much solely focus on skyscrapers. I just came back from a trip where I took photos of about 500 skyscrapers in several cities. Before the trip I really thought about replacing my aging camera, but the trip changed my opinion. The camera did everything I wanted.
As as do not have a mirrorless camera yet, I only know EVFs from photo fairs where I tried cameras like the R6, R3 and R7 as well as the Sony A1. The only EVF I saw so far that was not completely bad was the one of the R3.
In poor light with a mid-aperture lens, OVFs are massively darker than an EVF. I actually recently did a test with my R5 and my D750, and put the same f/3.5 lens on both cameras (Nikon AI 135mm f/3.5), and took pictures through the viewfinders with my phone - and found the OVF of the D750 was over 7 stops dimmer than my R5's EVF. Here's a picture - left is the R5's EVF. Center is the view from the OVF at the same exposure.....and the right is the OVF with the expsosure adjusted, which was 7 stops different with regards to ISO and shutter speed.
Of course the EVF shows a brighter image, because the brightness is amplified. That is not a real image any more through. Even if I take photos at low light, there usually still is enough light to allow me to see the subject through an OVF. If it gets too dark, I usually stop taking photos. With my DLSR I tried long exposures in virtual total darkness. I used a higher ISO setting, because otherwise it would have taken hours. The result was quite unusable. A lot of pink light at the edges of the photo. It seems if the light is too low, the noise just get overwhelming. That was quite shocking to me, because with a film camera I never saw that effect.
My problem with EVFs is that they disconnect me from reality. Instead they show my a high resolution copy of reality. With am OVF I still see things with my own eyes. The lenses just bend the light a little, but it is still the original light. The image in an EVF however is the same no matter if you watch it live or watch a recorded video later. I do not want to travel to another country and then only see a digital copy of reality there while I look trough my camera. Actually with a mirrorless camera you do not even look "through" your camera any more. Imagine something very memorable happens while I look at the EVF. Then I only saw a digital copy of it.
It seems these days you have to buy a very expensive medium format camera, if you still want a mirror. That is very sad. On a planet with eight billion people there does not seem to be enough demand for affordable cameras with a mirror any more.