What verb goes with singular pronouns?

Asking this on behalf of a jelly who can’t post questions right now.

If we’re going to be using “they” as a singular pronoun, why are we not using singular verbs? Doesn’t it make more sense to say “they is” if it’s singular than “they are”? Arguments that it’s not correct grammar fly out the window as soon as we redefine “they.”

For that matter, why not redefine “it,” which has the advantage of already being singular? It requires fewer contortions than assigning a different number to “they.” It’s no insult to call a person “it” if we extend the meaning of the word, just as we’re apparently doing with “they.” Also there’s a precedent, because infants are often referred to as “it” even when we know their physical gender: “Give the baby its pacifier and maybe it will stop crying.”

In my opinion, it would make the language adaptation easier to normalize.