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.
Normally it should not have been, with cache and all, but that was the past...
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...
Not really? .com and .net are still up
If Let's Encrypt goes down, half of the Internet will become inaccessible in a week.
DNS is barely centralized. Is there an alternative global name lookup system that is less centralized without even worse downsides?