If you think you’re wasting your time reading something purely for enjoyment… You’re not.
Even if the only reading that truly matters, that is truly worthwhile is nonfiction. Be it textbooks or self-help books, technical books or cookbooks, then reading fiction for fun matters.
Because reading is a skill like any other skill. And, like any other skill that requires practice, reading takes practice. And, like any other skill, if you don’t read, you can get rusty.
But if only reading nonfiction matters, then you need to read fiction to hone your reading skills so you can better read nonfiction. Because if there’s going to be a time when you “mess up” reading - a time when you immediately forget the previous paragraph or a time when you can’t remember where you left off - it should be something that didn’t matter.
Of course, I don’t think reading fiction doesn’t matter, not even in the context of acquiring knowledge and skills.
Reading is essential. And you don’t need to spend a ton of money to read. Your local library has books you can checkout for free - or nearly free. If ebooks are your thing, again, through your local library, there’s the Libby app.
Or simply search “free ebooks” on Amazon - although you’ll have to wade through endless romance novels (unless that’s your thing).