To be fair, DMARC has been required for a very long time. IIRC Google warned about 2 years ago circa that non-compliant emails would land in spam or be null-routed. And the DMARC noise started even before that.

Gmail only requires DMARC for senders that send >5000 emails per day. Below that it's not required. That rule only appeared in 2024 so I wouldn't say it's been required for a very long time. Perhaps you're thinking of DKIM, which is different.