This is missing the point.
To be clear, I'm not necessarily a fan of DMARC, particularly how it was introduced. But it is very obvious that spammers will eventually do everything to not be flagged as spammers.
What DMARC gives you is that it makes it less likely that your phishing mail will come from contact@yourbank.com. It will rather come from contact@y0urbank.com or some other domain.
How much of an improvement that is and how many people will notice is certainly debatable. But that's what DMARC can give you. Nothing more, nothing less.