I want to push this discussion to a more grammatical reason why E is wrong. Although passive voice is certainly not the preferred way to say something, passive voice is not necessarily wrong on the GMAT. The clear grammatical reason why E is wrong has to do specifically with the " ,by shoppers" part of the sentence.
First of all, by putting "the shoppers" in commas we are indicating that it is a subordinate clause and can thus be removed from the sentence without losing any meaning. "By shoppers" is actually a pretty important part of this sentence, however, because it contains the subject. As a result, I'd advise us to keep it out of the commas.
Second, and perhaps even more grounded in grammar, by putting the modifier "by shoppers" between "of" and "as", we are introducing a prepositional phrase into the middle of the idiom "thought of ______ as." As a result, the idiom breaks down.
Hope this helps!
Brett