Which is exactly what happened to Slack, and took them offline for most of a business day for a huge fraction of their customers. This is such a big problem that there's actually a subsidiary DNSSEC protocol (DNSSEC NTA's) that addresses it: tactically disabling DNSSEC at major resolvers for the inevitable cases where something breaks.
As if DNS isn't a major contributing to A LOT of downtime. That doesn't mean it's not worth doing not investing in making deployment more seamless and less error prone.