What you see there is 20% if the Busy design potential. We are far from having our final design product. This is an Alpha version in which we focused on main features like posting, voting, and not the design/interface or real user experience.
90/2000 i'm not sure if you know what you're talking about. Unless Facebook, Slack, Rocketchat, are from 90's, dont get me wrong, this is the design trends 2010-2015, not 90-2000 even if i could agree on the fix sidebar/iframe early 90 style. But we could discuss this for hours. I've seen Akasha and it does not surprise me at all, wait & see Busy in few month after our redesign...
you'll be surprised ;)
Also i'd like to add that ordinary users dont necessarily like futuristic designs.. they mostly like to use what they're familiar with.