My understanding is that should not means that you should not try to retry. If I do retry than the other party can rightfully claim that I am DDOSing their service, trying to send emails to deleted accounts or put me on a spam list. I do not think that ignoring the RFC and trying to cover up for Google is the best course of action here. Maybe, just maybe, this is the right time when people realise what does it really mean to have an entity like Google. Because as it is stands, we are going to have the DNS infrastructure moved over to them with DoH and a similar outage is going to be even more devastating. The internet was designed to be resilient to failure because of its distributed nature and right now it just shows why concentrating resources in one place is bad.