If you cannot see the back LCD on your DSLR maybe it is not a good time to take pictures or video? Or you should stick to film that has huge room for bright highlights in full sun? 95% of my best digital outside photos or video are taken when it is not bright overhead sun. So instead of a new camera with EVF or reading the zebras to make sure your highlights are not blown you should just take your shots or video when the light is good? Even if you turn down the exposure on digital so you don’t blow your highlights in full sun you have to pull your shadows up so much that you get a lot of noise. The best digital cameras like a Nikon D850 only have about +2 stops of highlights before the pictures are unusable. The best film like Portra have about +4 stops. Many times when the photo is overexposed a stop when you try to improve it in post you just don’t get a good result even using raw.
The flower below was taken with a digital camera about an hour before sunset and mostly in the shade.
The shot below is what happens to many digital photos when taken at mid day.
On the other hand here is some film shot at mid day with full sun.
Right now you have a ton of people switching to buy mirrorless cameras from DSLRs to get an EVF. That way you can control your exposure better when you can’t see the back screen. My suggestion is that if you cannot see your back screen maybe your camera is telling you it is not a good time to be taking pictures.
Now if you are switching to mirrorless because you want to take more videos with your camera then I think that is a good reason. But if you are going to take mostly or all photos and not video there is no reason to ditch your DSLR or not buy a new one. Both Nikon and Canon offer very good DSLRs at modest prices. I have a several year old Nikon D5500 that takes sharp clear detailed photos and is half the price of a comparable mirrorless.