Do we have a means to find samples of past users of Hive/Steem who have left over the years for surveys? Or even people who landed on sign up pages but did not complete the process. IMO that is a crucial element, because only surveying those who successfully signed up and then have stuck around is going to have major survivorship bias (which I find to be a big limitation in my own ability to analyse these issues primarily based on the data on the chain itself).
An alternative approach to surveys if we can't find sufficient people for samples (eg. if one person in 10,000 is even aware of Hive/Steem at all) would be some kind of focus testing, eg. getting people to attempt to sign up and use Hive and see what their experience is.
On the matter of social media vs blockchain platform, it is a fact that at one point in the past Steem was indeed quite successful as a social platform, with steemit.com reaching the top 100 websites in South Korea by traffic. We can't even say with reasonable certainty - why was it initially successful and why did that success so quickly disappear?