Yeah and honestly, this is largely a reasonable standard for anyone running an email server. If you don’t have SPF, DKIM and DMARC, basically anyone can spoof your emails and you’d be none the wiser. It also makes spam much harder to send without well, sacrificing IP addresses to the many spam lists. I wouldn’t be surprised if some people setting up their own mail server were made aware of these things because of being blocked.
Definitely not just you, I instantly said “holy shit this is one ancient meme”. I remember it too from the early 2000’s.