I had the same thoughts, but Steem at least alone isn't capable of bringing something that could replace Youtube. Steem actually only allows text, photos and videos have to be linked. This is b/c the blockchain would become waay too big if you even allowed photos in posts let alone videos.

We need an open source decentralized way to upload videos so they can then get linked (maidsafecoin?) and then an interface like steemit could come in with steem's monetization system. Ads wouldn't be necessary anymore but if you do use ads no more middleman taking a huge cut, but monetization directly from user engagement really has the least middlemen and is best for content creators and content quality.