Am I thinking about this incorrectly or is there a legitimate argument for changing the current grammatical norms?

You are thinking of it incorrectly. Language shifts and grammar shifts with it. Grammar “rules” are guidelines on how language is most commonly used to get ideas across.

It’s still important to teach grammar because it gives someone the tools to convey their ideas in a way that most people will understand, but outside of a classroom it’s pointlessly pedantic to correct someone’s grammar unless their meaning gets muddled.

So maybe usage will shift enough that “deers” will be the new standard plural maybe not, the important thing is you know what they meant when they said “deers”.