It was obviously meant to be decentralized but then some 40-50 people initially gained or bought large stakes in the platform and the future of steemit basically depends on those few people way more than the other 100k users.
So it definitely has a power structure to control major aspects of the site.
But here's the problem, at what point does a decentralized platform become centralized, what fraction of users should own what percentage of stake in it for it to be called "centralized" ? It may be 50-100 users now with substantial powers to steer this thing the way they want, but those numbers obviously aren't going to stay like that, they will grow and the ownership will get further distributed
My point being, you can't really classify something as either this or that, its not as black or white like that.