>People aren't born not wanting to have kids, since all their ancestors did.

What evidence do you have that all their ancestors wanted to have kids? I can think of a lot of reasons why people may have had kids without necessarily wanting them. They wanted to have sex in an era before birth control. They were pressured into it by the social norms of their local community. They were raped. Etc.

I have a lot of criticism of the childfree movement but I think it’s pretty disrespectful to assume they’re not being honest when they say they don’t want to have kids and that they’ve always felt that way.

Birth control is older than the Bible[1], it just wasn't as effective. Humanity as a whole was very aware how babies come to be.

Ways to have fun without coitus aren't a recent invention either.

Human reproduction and raising children is an unusually taxing, time-, and resource-intensive process, which is why we've applied our considerable intellect to plan for that since forever.

[1] https://en.wikipedia.org/wiki/History_of_birth_control

Involuntary reproduction has been a tiny tiny minority of births for the past few millenia at least. It happens and is awful but it should not be construed to constitute a large part of any person's ancestry.