I don't like reading gentle and pleasant books. If I wanted to be purely entertained and accidentally stumble upon a deep emotional journey, I'd watch a movie or a TV show.
I'm reading something "light" now (or "lightish") and it's Alain de Botton's Essays in Love and I don't know, he's supposed to be a philosophical writer and the reviews of the book claim that his sentences are poetic, but I'm not impressed so far.
I think sophisticated writing is one of the most important criteria for a book to be a work of literature, especially modern literature. Did you mean the Peter Rabbit books? I don't really know much about them apart from the ubiquitous merchandise that they spawned but I'd say no.
The fact that you prefer heavier, more philosophical/intellectual books does not give you the right to redefine the word "literature".
There's nothing more boring than elitism.