I noticed you listed all fiction here. Do you ever try reading nonfiction? You might just need something more concrete to hold your attention rather than fictitious characters in imaginary scenarios.

Another thing I suggest to lots of people is to try audiobooks. It's not the same as traditional reading, but it's way better than not reading at all. Sometimes I use a screen reader on my laptop and follow along with my eyes. I've noticed this allows me to read something for much longer and the comprehension feels stronger.

Also, I wouldn't worry about finishing books if that's hard for some people. If something doesn't hold your interest, there's no point in slogging through it just so you can earn your imaginary 'finished' trophy. Especially for fiction.