As someone in the mainstream content marketing and social media marketing industry (day job, what's good), the barrier to entry is too high. Getting past the velvet rope is only like, 20% of that onboarding experience - then you have to wrap your head around all this stuff and meanwhile, you're thinking, "Dang. I just want to enter my email address and password in. Never mind."
GaryVee's content is compelling (and his following massive and properly mainstream) because it's accessible and interesting to people outside of the super exclusive online club comprising social media marketing professionals.
Being a STEEM noob, I don't have the context or history with this platform to speak to its maturity, but I will say that it is, from an outsider's POV, positively hyper-niche.
It'd be interesting to find out how many people stumbled upon STEEM looking for a content creation/social media platform and signed up primarily to fulfill that purpose (with crypto rewards being secondary to the decision) — my guess is probably not many at all.
That said, I think the TravelFeed team is doing a great job doubling down on an audience in an effort to support adoption (and high-quality contributions) from the non-crypto curious.