They actually kind of fixed this recently, you can ask them to move your route53 control plane to another region in the event of us-east-1 breaking: https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/ac...

There’s a bunch of caveats but it’s worth enabling if you’re changing dns all the time (as most AWS networking doodads like to do).

Is there an architectural reason it’s not for replicas in the other AZs?