So, there might be a bit of a misunderstanding here. steemit.com is not a dApp, but not for your reasons -- steemit.com is an interface that access an underlying dApp (the STEEM ecosystem with posts, votes, and rewards). It's also not the only interface to access it.
But currently, steemit.com is not decentralized. When you access steemit.com, you outsource verification of the content displayed to Steemit Inc.
Indeed, if you were to download (and vet) condenser and run it off of your own
steemd node, which is validating data, then you are accessing the STEEM dApp without outsourcing verification.