Blockchain-based DNS would allow people to actually own their domain names instead of just renting them for an annual fee.
Domain transfers could be effected on-chain for a fee. Spam prevention is built-in because any action recorded on the blockchain incurs a fee. The fee is determined by the free markets and nobody holds a monopoly over the market.
People who trade domains would end up subsidizing those who hold domains; allowing them to hold domains for free, permanently (once the domain is bought and initial transfer is made).
It removes the need for an authority like ICANN who decide who gets to control what.
You don't have to limit yourself to one blockchain, new blockchains could launch and be treated as distinct gTLDs.
You don't need Certificate Authorities and the complex, trust-based infrastructure to implement certificate verification. It can all be done on-chain, anyone can sync their own nodes to verify who owns what domains.
Blockchain is naturally good for high-read scenarios. It can scale in terms of number of reads without limit; just add more nodes. The writes are limited, however, transaction fees serve as a natural regulating factor; it can always meet the demand, for the right price; which is determined entirely by the markets and based on usage of computational resources, not based on monopoly pricing.
Bitcoin, with a measly maximum of 4 transaction per second, has already proven that transaction fees can stay reasonable, even with extreme levels of hype on a global scale.
BTW, if you managed to read my comment, you can consider yourself lucky because this perspective I'm sharing is consistently suppressed and heavily down-voted... You can be sure that there are financial interests behind the current DNS system which do not want to leave room for any tech which might liberate the internet from the clutches of the incumbents and which might force them to compete on a free market.