this song is about society.
"us" refers to the current generation. we feel hopeless to solve the world's problems (rummaging for answers in the pages) because motivations for the betterment of the human species as a whole are repressed by an overwhelming greed for power and profit (we're living in a den of thieves).
"they" are the future generations, far more enlightened than we, who look back on this time as we look back on the dark ages, recognizing that we had it all wrong, and building a statue to recognize our time as a very trying one in human history.
we often succumb to the conveniences of the established greedy, capitalist structure because those in power make it very difficult to change (and it's contagious).
this song is cynical and despairing in it's sentiments of the world we know.. yet assuredly hopeful for the world of the future.
if you feel the same way, go to thezeitgeistmovement.com