fiction absolutely can be intellectual. 1984, 451 Fahrenheit, anything dostoevsky or heinlein.
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.