I found it harder to immerse myself in a book about 10 years ago. I read less comprehensively and for much shorter periods. I also think I tended to skim/skip a bit more. I assumed it was a stage but it carried on for years. This was with paper books.
I actually read 'better' with an ereader oddly enough. I rarely skim or skip, and generally read for longer periods before getting tired or antsy.
I do read much faster on a computer monitor, but I know I skim a lot more and sometimes have to go back due to some weirdness where the words do not seem to reach my brain. Could be online reading, or could be just old age
Helen