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I and I am sure many "oldsters" on this site have similar problems. I have a severe cataract in my right eye and am using the "Russian formula" N Acetyl Carnosine--2% as found in Can-C eye drops. But that only marginally helps cataracts and might take years of eye drops. But I am trying to find info on the multi-focus type cataract eye lens replacements.---I know the problems of being one-eyed and having to use my left eye rather than the right eye (It even affects physical balance).----But it is possible. Yet I also agree---most cameras are not made for manual focus. Some "mirrorless" magnify which helps.

Here is my suggestion if auto focus fails with you.------Use a lens on your particular camera body from before AUTO FOCUS---so that it has a good---l o n g---focus scale and do as we did for the century before auto focus------MEASURE THE DISTANCE AND SET IT. I use my first 35mm camera from 1953 with a wonderful fast lens and excellent distance setting scale with "circles of confusion" markings. (It does not have split-imaging focus, either) I call it my "camera which never took a bad picture." It works as well today as it did in 1953 when I bought it with my own money.-----Eric

I think the answer has to be how to better utilize the autofocus capabilities of your camera.
Depending on your eyesight, you COULD consider an external monitor like video shooters use so you can better see what is happening. SOME CAN BE SET UP FOR FALSE COLOR FOCUS PEAKING.
If you want a fixed focal length lens, something like 35mm will give a nice field of view and a bit more DOF naturally. Wide and fast make focusing easier than long and slow.
Consider how best to set up your camera for impaired vision.
Experiment, Put on a fast wide angle like 35mm f/2, try setting the camera to full auto and take a bunch of pictures. Ill bet you get sharp pictures.
Then try other modes based on your experience and preferred way of working.

In a different way, I sometimes shoot with my daughter who is a wedding and event Photographer. My job is usually to provide " color" shots of people and things, sometimes from unusual angles, while she is getting the money shots. I often shoot with a fast 35mm on full frame with my camera set to BBAF. There are many times I shoot WITHOUT looking through the camera. Since I know the field of view of the lens well, I just point to the middle of the 'frame' I want, touch BBAF & shoot. They are always in focus.
So don't despair, there is a wy to make your camera work for you. Don't give up.

My vision was 20/400 30 yrs ago. Probably not as bad as yours. I use a different viewfinder cup to block sunlight. I still shoot events, second shoot weddings, concerts etc. I go thousands of shots without any out of focus. It's probably not the lens and I don't know how much you know about AF modes, adjusting viewfinder brightness on your mirrorless, diopter adjustment, dof control etc. So, my intent is to not be condescending. Simple answers - I shoot with dslr's, d750, d7100. Primarily 24-70 2.8, 70-200 2.8, both Nikon. I actually trust my camera! Shoot manually with high enough shutter speed ie 1/200 and above. Turn on your focus confirmation beep (unless it's intrusive). AF-S,S is the mode that allows the beep. If there is a lot of movement, no beep will be available but AF-C, D9 or S. Low light indoors, same thing with autoISO. Here's a few pics from two weeks ago. I also use my "OK" button from 100% zoom when chimping on image reviw (group shots checking for closed eyes etc).