Plants came before moths, but there are some desert plants whose life cycle is dependent on a species of moth pollinating them. How things were in the past influences but isn’t the sole arbiter of how things are in the present or future.
Which isn’t to say that it’s strictly true, I think it serves more purpose as a thinking exercise than a scientific theory. But I don’t think it’s impossible that it’s true, either.
Yeah, I don’t think the OP was saying every plant in existence is dependent on humans. But crops are, and we’re dependent on them. Co-domestication, I guess.