Steem/Steemit may not be sustainable in it's current form, but should there be a true impetus for change (like a large investor coming in or something like that), it would be fairly trivial to fix nearly all of the major issues with the platform.

People ignore the most important things that this platform has going for it - a large and active user base that creates a ton of content. We just need a way to filter and present content in more easily accessible ways, remove the barriers to new user signup (i.e. waiting a week to get an account), build more effective ways to deal with spammers and abusers & tweak the rewards system so that whales and bid bots aren't the only way that new users can prosper.

We already have a more viable model than 99% of the blockchain tech that's out there now, and I see huge potential once advertisers are able to promote content and ads.