As you have correctly pointed out, most users on Steemit still think Steemit is synonymous to the STEEM blockchain. They still fail to understand that STEEM is a platform. A platform with open APIs for developers to build applications. A platform with data stored on a public blockchain. STEEM provides a framework for apps that heavily rely on content generation and social interactions.
It is easy to say that there are potential STEEM-killers. However, as of now, there aren't any decentralized social network that is as developed as STEEM. Even if there is, STEEM has already started to gain traction and network effect, making it very difficult for any competitors to catch up. Network effect is key for all social networks and that is why Google Plus is never able to catch up with Facebook.
The STEEM network is the most heavily used blockchain based on stats from Block'tivity. To further illustrate this point, I recently made a post to understand when are STEEM users most active on a typical week. Through this, I was also surprised by how many articles are being posted each day. At the peak of the selected week, we are seeing 2324 new posts created in an hour! I think stats and data speaks louder than words when it comes to this debate on STEEM's competition.
With upcoming changes like Hivemind and SMTs, STEEM is just going to further the gap with its competitors.