I don't exactly remember where I found it but there are also some problems when it comes to IPFS. A blockchain is a slow database but it has its advantages as they truly can't be taken down by anyone.
There are challenges, certainly. But remember ipfs is an open source protocol. Tube's ipfs system is 60% original code. So if there are problem with ipfs they are all situation specific. If you find a link on what you're talking about maybe I can clarify. Anyway we wouldn't be using ipfs otherwise, we're not stupid.
As for blockchain, you clearly don't understand how a blockchain works. The point of it is that every node has a copy of the entire chain to verify the validity of the data. So how would you like to store petabytes of data on every computer? This is not the purpose for blockchains. You can store the metadata on a blockchain but the video has to go on a server, ipfs or torrent. Besides if your app+content lives on the wider ipfs like bittube, it can't be taken down either. Videos can be unpublished but it's never truly gone if u have the ipfs hash.