Marketing is simple, you pay money, you get users. Anything that does not cost is called PR.
Look at the TikTok app, that's been around since 2012, but it's only once they started advertising it on other apps that they started to grow exponentially, to the point that they now have over 900 million users.
The community doing little things on Twitter and telling friends and family, or advertising on billboards by the highway, will bring a negligible amount of people in.
If Steemit inc spend money to market, the Steemit community will grow, if it doesn't it won't.
Best places to advertise:
Google
Facebook
Twitter
Instagram
In-App advertising (similar apps)
I have been saying this for 3 years now, one day, someone might actually listen.