It's not about having the time or not, it's about what you choose to read when you
do have the time.
The difference is that when you read fiction, you are in a world, a physical land that is entirely constructed by the mind of the author. The characters aren't bound by the same laws of physics that you and I are. When characters make decisions, the other characters react in the way the author wants, but real people may not react that way.
With nonfiction, there are rules. With fiction, there are no rules. In fact, you don't know what the rules are when you read fiction.
You know that quote about those who don't read history are doomed to repeat it? Well, there is a lot of history to read.
They're two different universes. One, fiction, is framed in a universe where we don't exist. The other, nonfiction, is in the same universe we all share here. In fiction, what goes up may not come down. If you shape your life or make decisions based on fictional ideas, they don't always apply in the real world. Sometimes they may, but mostly they do not.
Yes, you are right, lots of insights can be gained from fiction. I learned a lot reading slaughterhouse five. It's fiction, but it's also pretty real in a way. I learned a lot from 1984. I learn a lot from science fiction.
But there are is also a lot to learn and a lot of insights to be gained from nonfiction as well. Truth is stranger than fiction.
Think of it this way. If you only read fiction for the rest of your life, could you program a computer? Could you build a house? Could you understand quantum mechanics or any myriad other practical skills? Probably not.
This of course is my opinion, but if I had to choose between a future life of only fiction reading or a future life of only nonfiction reading, I would choose nonfiction. I think nonfiction is a better learning tool and a greater benefit to my life than fiction, because through nonfiction, I can learn facts that I can't learn through fiction. It's actually difficult and confusing sometimes to decipher truth from fiction.