I think engaging with works of fiction is just as important. Like anything, if a work of fiction engages and challenges you, and you are an intentional reader, it exercises very important muscles.
in fact, by adding that intellectualism is what makes these stand out.
But i do specify non-fiction because I wouldnt say most fiction is intellectual; or if you try to approach some fiction you'll quickly dig deeper than what's actually there and then it's just you superimposing.
The example i like is colour metaphors. Shakespeare will say that a character put a green shirt on. You're supposed to say 'thats just a new shirt, not the colour green' but no. It actually really is just the colour green. You cant dig too deep on most fiction.