No DMARC is about telling receivers which of SPF/DKIM are valid, what to do with it when it fails, and where to send a report to. Oh look.. like Mike said.

To be clear, I am saying this is incorrect.

DMARC is primarily about "alignment" (switching SPF from caring about the envelope sender to instead using the from header). Yes, it does also tangentially address those other points, but the primary reason it was adopted was to prevent spoofing of from headers (where in original spf that was a non-goal)