That’s just not true. There’s a reason we all study grammar, and that’s so we can all learn the rules that have been built up along the way. Without that, we’d get more severe language drift, which gets in the way of the primary reason we have language to begin with: to communicate. So the proper form is the form we’ve all essentially agreed to.
You’re right, just someone who is really into linguistics as a hobby. So I’m not coming from an academic background (e.g. study of how languages change), but rather a practical side (how languages work). I love studying grammar, especially from very different language families. So for me, grammar is incredibly important because it’s how we keep communication consistent across diverse populations, and changing it regionally gets in the way of that.
But language is constantly changing, there literally is no “proper” version of any language, because any “proper” version is going to be biased toward the dialect spoken by whichever group created the “proper” version of that language.
Published grammatic standards, e.g. the MLA handbook, are for specific use cases and do not define the language itself