I don't agree. Text as the primary content can be very visual with good graphic design. It's hard to find pictures that are informative and not merely illustrative. Non-informative pictures just distract and feel condescending.
Maybe non-informative pictures just distract you, and feel condescending to you, but everything I've ever read besides your post indicates pictures are the way to go to attract and keep attention in general.
Could be your reaction is indicative of the target audience's? I doubt it though.
An email from David Wood, organiser of the Humanity+ UK 2010 conference in London on Saturday 2010-04-24:
I plan to make such a poster, and I'd like the advice of people here. Trying to represent what Less Wrong is about in the space of a poster could be challenging. I have maximum space equivalent to sixteen A4 pieces of paper. In the spirit of not proposing a solution until you've had a chance to think about the problem, I'll put my current plans into a comment.
Update: looks like it will be Roko rather than me making the poster, but the same applies, your ideas could doubtless be very useful!