The Tolkien work I struggled with was The Silmarillion. I understand it’s not much like the others and was a posthumous publication, but middle school me struggled to stay interested enough with the way it was structured.
Most media from the 1930s to 50s isn't popular anymore. Taste move on. Idk if you can simplify this to attention spans.
Quitting my corporate gig has also been massively helpful - our big tech overlords were committing Guantanamo level atrocities on our minds via Slack overload, and I will never return to that kind of environment. I'm barely exaggerating.
If you're a podcast kind of learner, Huberman has an episode on this "dopamine fasting" concept.
Start with books you can focus on now, gradually move on to more complex works. Don't feel bad about picking a genre which really draws you in. You don't have to read Dickens on day one (although he is a great writer, older works ask a lot in terms of focus and frame of reference, including some understanding of society back then and there), and it's fine to indulge in Young Adult fiction if that works for you (Harry Potter not too demanding to read, and pretty good too).