Computers have so much RAM now, there's no need to write efficient code - it's free real estate!
You might change your tune if every lookup starts talking a second or two to read through the DNS entries... Anyway DMARC isn't that complicated. You make it sound like regex or brainfuck.
edit: and it's getting simpler, too! Funny about p=reject being mostly discouraged now, I almost never use it anyway, and I can't lie I felt a little called out over pct=100 😅