For the most part, I agree - it's very high-school-English-course to say, "The red dress represents passion," and "the book is a symbol of knowledge," and so on and so on. It is elementary, I afgree, and probably an overused, trite crutch of shitty writers. But I noticed while reading Lolita (pre-lecture) a point at which Nabokov wrote a very skilled, very beautiful, very complex, but nonetheless symbolic scene right before Lolita seduces Humbert for the first time, but after both parties have made allusions to the event.
"When the dessert was plunked down - a huge wedge of cherry (the wet, juicy red fruit is an embarrassingly obvious, overt reference to Lolita's naïve sexuality) pie for the young lady and vanilla ice cream (again, thick, opaque white ice cream is a fairly unmistakable symbol of Humbert's sex drive) for her protector - most of which she expeditiously added to her pie (Lolita taking and consuming his ice cream takes the whole thing one giant, uncomfortable step further)..." (122)
I noticed this while reading and marked the page intending to read it again, because I thought the symbolism was so well-done. It didn't follow a lame, trite, x=y formula, even though the presence of such sensual, dripping fruit could have very easily rendered the scene hackneyed and predictable. So it was surprising to me to hear that Nabokov was so critical of the concept in general. Obviously this vivid description of the meal has significance of its own aside from its lurid similarity to the body parts involved in the preceding scene... but it still makes me wonder. Maybe he criticized others' unskilled attempts at it but considered it acceptable for his own use? I guess that's what the title of this post means, but I found this fact useful, especially after falling in love with the passage.