It is a gender neutral pronoun.

Also when talking about people, it would be nice if they was a lot more normalized even in situations where the gender of the person is known.

But “it” is for inanimate objects. “They” is a gender neutral pronoun for living creatures.

But “it” is for inanimate objects

Not quite. “It” is a general reference pronoun with a function akin to “the”. It can be used to refer to anything that is a thing, even if said thing is animate and/or living.

When referring indiscriminately to a specimen of fauna, “it” is a linguistically appropriate identifier whereas “they” would only really be entirely appropriate when referring to an individual or subset of individuals, regardless of species or animacy.

Since this fish has no distinguishable identity apart from the cultural impact it may spawn, I reckon it’s more appropriate to use “it” but “they” could also work.

I am not a linguist. But if you are, feel free to correct me. If you feel like pretending to be a linguist, go talk to an LLM cause IDC.

If you wouldn’t call a human being “it”, then you shouldn’t call a non-human animal “it”, either.