I suppose there could be a blacklist that gets periodically downloaded by the OS. But then you're back where you started - who maintains the blacklist?
You can easily control the domains, schedule their use, and not worry about takedowns.
Although I'm not entirely sold on BlockChain, there are other more energy saving gossip based Byzantine fault tolerant protocol to consider for use. However, everyone is just prototyping in this space. So for one I'm big supporter for the Root Files to be stored in this fashion, even if it is on a blockchain.