DNS is a centralization risk, yes. Somehow we've decided this is fine. DNSSEC isn't the only issue - your TLD's nameservers could also be offline, or censored in your country.
Even the current centralized ICANN flavor could be substantially more resilient if it instead handed out key fingerprints and semi-permanent addresses when queried. That way it would only ever need to be used as a fallback when the previously queried information failed to resolve.
The only thing a blockchain is good for is achieving decentralized consensus on what value a key points to, which is what DNS is.
An alternative way of looking at this is that acquiring domains must be somewhat expensive by definition; either you enforce it at the system level, or you make it free, but then somebody will inevitably grab all the interesting ones and re-sell them to others. A blockchain is the only way to make decentralized financial infrastructure viable.
Think about what would happen the day that letsencrypt is borken for whatever reason technical or like having a retarded US leader and being located in the wrong country. Taken into account the push of letsencrypt with major web browsers to restrict certificate validities for short periods like only a few days...
Long version:
If you're so popular all around that you really really want a very very short TTL, people will query all the time from all the places that "count", won't they? So it's gonna be cached.
If you're not so popular or not all around, what does it matter even if you had a very very short TTL? You're not loosing much.
I haven't followed this closely, but have there been any... shall we say plain outages longer than six hours? That's not an outrageous TTL. Or a day.
If Let's Encrypt goes down, half of the Internet will become inaccessible in a week.
* https://www.keyfactor.com/blog/2023s-biggest-certificate-out...