It's not a black-and-white issue. There is compromise if a person doesn't want children right now, but is genuinely open to it when there is more career stability. Some people may also be open to children, but not at the expense of giving up one's career (some couples have worked it out by having the man de-prioritize his career for a while).

I do agree that people can waste time if a person says they "don't want children right now," but really mean that they "don't want children ever." In either case, there is no harm to clarify this before going right to breaking up over hesitations.