I think this may be an unintentional consequence of two things;
Watchtower literature is written by the uneducated, for the uneducated. If they put anything remotely thought provoking in there people become frustrated because it's "over their head". The literature is meant to be read and understood by people with naught more than a gradeschool education. So why did we feel zombie-like? Our minds weren't challenged.
The Church has had vast resources, and paid some amazing musicians, to write music for them. For a long time, if you wanted to make money, the only thing you could write about or depict in art was religious crap - because the church and the King were the only ones buying. The WTS doesn't have those kinds of resources, so their songs sound like something a 6th grader with a keyboard might come up with.