Dream Sequence:
What general sorts of things are you imagining as specific ideals that define the 21st century? I guess what I mean to be asking here is about the sort of tone you'll be aiming for. A lot of people might consider a game where the Spirits are manifesting ideals like Cynicism, Outrage, and Paranoia to be a quintessentially 21st-century game, which would be a markedly different sort of endeavor from one where the defining traits are things like the Optimism and Ingenuity that you mention in your quote.
Quoted for emphasis. I've been itching to ask a similar question, I just didn't feel like I could express myself properly without sounding like an asshole.
Having read what Dream Sequence posted, I felt like I could add one thing though. Young Centurions has the benefit of hindsight. We now know what made the 20th Century awesome (by which I mostly mean Post-Punk). We can only imagine what the nature of the 21st century will ultimately be. People in 1919 probably thought they'd be done with war for a long long while after the great one. People might also disagree on what constitutes the best or even just a positive trait.
Some kind of outline for orientation might be useful here.