Maybe more useful, but I think purely utilitarian writing does less to broaden a reader's mind than more ambiguous writing that they have to struggle with. I know it did for me. But I understand what you are saying, and I too outgrew reading "challenging" novels because I feel like my mind has been broadened enough and also I feel like I just have less time (although maybe I am just getting older).
I haven't read this essay in a while, but as I remember it Jonathen Franzen's essay "Perchance to dream" takes on this exact subject and is an excellent read. Regrettably it is not available online.