I always found this argument funny because how would you use pronouns for someone whose gender you do not know? They. It's they. E.g. you are given the sentence: Jordan went to the store to buy apples. And you want to ask a followup question regarding how many, you reply: How many apples did they buy?

And that's not how English was taught to me or 99℅ of the population (including English as a second or third language) 20+ years ago. Singular they was only used for situations where the gender (read as superficially visible sex) was factually unknown. You see a forgotten umbrella and never saw who forgot it: "Somebody forgot their umbrella." As soon as you only got a glimpse on the person forgetting it you would make a guess about he/she.

They has been used for gender ambiguity in everyone's lives since grammar school.

If you're younger than ~30 and from Great Britain, maybe. GB were the first to formalize and teach it like that less than 2 decades ago (if I recall correctly).

People just have an inherent bias towards trans folks and it's incredibly depressing and sad.

That's bullshit projection.

I, a non-native speaker, complain about increased ambiguity of the language because of singular they as a personal pronoun and make a proposal about new pronouns for the purpose.

You: Ah, must be transphobe. Let's ignore everything he said (which doesn't relate to transphobia at all).

It's so frustrating not to be able to have a discussion about stuff making a language harder than it needs to be without people invoking transphobia, like, instantly.

But hey, I called it: can't have a discussion about it and I've given up on it.

edit: tiny add-on. I was still taught gender-neutral he and only heard about they later while being discouraged to use it in writing.