HIVE

Uncle is of indeterminate gender until I learn otherwise.

Then, why not it ?

Because Uncle is a person, and we don't use "it" as a pronoun for people. It's reserved ("it" is) for things that are subjects or objects of sentences that are not sapient beings (in this case "it" has replaced "'it'").

But less sapient "things" like animals are also addressed as it

"less sapient 'things'" != "sapient beings"
"less sapient 'things'" == "not sapient beings"

Well, depends on how you define sapient. Its definition evolves as science progresses. So does this gender stuff.

My dude use whatever the fuck you want; I'm not using "it" for people, that's just demeaning.

They is incorrect. It's plural. It's misleading and creates confusion especially if you use it alongside something that refers to actual plural.
There should be something different that either is singular or does not create confusion, a new word/pronoun, perhaps.

Bruh, this is an argument that is just moronic because what you just said is actually wrong. They is nonspecific singular or plural. Just like using "formal" Vous in french (the only other language I know to relate to). If you speak English IRL then you actually use singular "they" all the time and you just don't realize it.

You might say something like "Did someone leave their books here?" or "Tell them I called!" Corporations and other 'group' entities are also "they" because what else would they be?

Well, I'm not a native but I definitely don't use they that way.

Well trust me, all native speakers do. We have a shortened slang version of "them" that shows up in a bunch of slang idioms: 'em. "Get 'em outta there!" (sports) is a good example.

In your native language you have specific different pronouns for singular and plural they? Do verbs conjugate different for them?

Also in English "it" pluralizes to "they" so you can make the case that "it" and "they/them" are the same word.

But get them out refers to more than one person does it not?

Yeah, we have different conjugations depending on the pronoun. He and she have the same form. We don't have a true/different neutral pronoun but a mix of masculine and feminine as some nouns are neutral if their plural form is feminine and their singular masculine. So, when we refer to a chair in singular for instance, we say he is broken. When in plural, it's they (but the plural of she which you don't have in English) are broken.