Up until now social media hasn't been a particular priority of blockchain technology- everyone's just been focused on the cryptocurrency aspect of it. If anything, cryptocurrency is actually holding back the development of blockchain as a viable technology, because everyone just wants to be the next big coin and make a bunch of money, and it's reducing diversification. (Not to mention outside interest in it.)

And yeah, I'm only aware of a few other blockchain based social media platforms- a couple of steemit clones in other languages and a terrible ethereum based one. There's really no other interesting, original blockchain social media networks. (Not that the world necessarily is into many more social media networks- it's proven pretty intolerant to new ones recently, and steemit only made it because it has its own unusual niche.)