Steemit will never be as popular as any of the sites you mentioned because on Steemit actual creativity not plagiarism is required so the majority of the human population will be cut out from making posts here (because humans aren't all equally original and creative, mostly just innovative at best) but because there is a financial aspect to posting here, the more users there are the worse it will become. Flooded with copyright infringing posts and endless resteems of more popular people's work. Which is how all of the websites you mentioned actually work.