I like the communties angle but I think you need to identify some areas to target and incentivise some community leaders. Certain groups like car forums or official sports clubs forums where they currently have fairly poor infrastructure for example and an incentive could be given to establish.

The UI needs to be simplified and improved massively though. A decent app is essential and some changes to the power ups etc. Despite being around for a while I've still got no idea what steem power is and who would want to power up or down. It needs to be the simple up / down vote and some engagement / retention mechanism so people get something extra for sticking with the platform. People just want to use something, not have to learn how to use it...