Decentralized control of a centralized finite resource (domain names) requires consensus. For example, Joe Smith and Joe Blow both want joe.com.
You want a protocol that gives consistent "global" state without any centralized / trusted users - blockchain/bitcoin is one of the only technical solutions to provide that.
I agree that it's a garbage solution in practice, but that's why it's got cryptoshit bundled in.
A potential different solution to DNS monopoly, if that is a problem that needs solving, is multiple name-resolution providers that have differing records on what name points where. (The tradeoff is that an owner may need to register their name with multiple different providers).