Earlier quoted context omitted.
Computers haven’t worked well without external dependencies in a very long time. How long can you perform useful work without DNS?
Extraordinary amounts of work are done without DNS. And even if it weren't, this is nothing like DNS because you can choose your own DNS servers and most people have a primary and a fallback. Where can I set trustd to use a different OCSP server? What is Apple's recommended secondary OCSP server?
A single point of failure, whether local or remote is an unfortunate design decision.