In addition to literacy skills practice, I've seen some research suggesting fiction reading might also help with empathy, maybe prevent cognitive decline later in life, and reduce stress. I hedged a lot there because Psychology research can be hit or miss.

I'd also advocate for a slightly shifted perspective: compared to lots of other ways to spend your time for fun, especially tech, smart phone apps, etc, reading longer form content can help to build focus.

If you assume not all of your time is going to be used for bettering yourself, saving the world, exercising, getting a promotion, or solving world hunger, and that some of it might be used for less fruitful endeavors like, say scrolling Reddit...

The comparison starts to look a little better, surely? At least your building the mental skill of focusing on one person/idea/world for a prolonged period and engaging your mental faculties in a creative way.