It's not plural though. It's just the third person neuter pronoun. Singular "they" has been a thing in English for centuries, and has only been controversial among a small segment of the population for a very short time.

Think of it a bit like French "vous". That's a "plural" (second person) pronoun, but is also used in the singular. In the French case, it's used as a singular formal second person pronoun in addition to a plural second person pronoun. Nobody in France is getting up in arms about how you shouldn't use "vous" when talking to one person.