> Capitalism only undervalues child-rearing if you fail to understand that the objectives of capitalism are predicated on the individual objectives of the entities within
I don't think this is true at all, since the ideological role of capitalism (and its class role) tends to encourage accumulation of capital above all else, so whatever can be made into capital-accumulating value will be, for instance over the past 50 years digital goods (and other otherwise freely reproducible goods) have been subsumed into capital - capital did this through its political arms, e.g the creation of copyright law. In the same way, capital may use its political arms to encourage 'family values', in a non-obvious alliance between the neo-conservatives in the 80s and the neolibreals. I understand value in the Marxian sense as a social relation, not value as in a purely "subjective" judgement. Value is both objective and subjective, in that it exists supersensibly but that existence is conditioned by a variety of objective social factors.
> Many women do not want to reproduce at all.
I find this line of argument relatively unconvincing, because it only works by assuming we are in total control of what we want, and that being ignorant of the origin of our desires, we assume them to come from within ourselves. It's a neat ideological point, but from social psychological perspectives is too simplistic to have much explanatory power. The point of my critique is that capitalism not only arranges society in a particular economic mode, but that this arrangement is therefore reflected in culture and society. Your argument is that capitalism gives the choice, and the choice is being taken, but this does not at all explain the context in which the decision is made in the first place, which is usually for economic reasons (whether the choice maker knows it or not).
>Many women, however, do want to reproduce, and the fact that women and men tend to diverge in their roles regarding child rearing is not simply something that can simply be asserted as being a consequence of capitalism.
I didn't claim that the difference in roles is solely due to capitalism, my claim is that the division of the roles between men and women works well with the liberal distinction between public and private - what is private ostensibly cannot be touched (by capital, by the state, by anyone) but what is public can be regulated by society in general (through the market) or by the government. The choices to remain an unmarried woman or to marry and have children are greatly dependent, before they reach the forefront of the mind, on the economic conditions of society.
The "family unit" is ideological, the free choice to "work hard" is ideological (see Weber's dissection of the "protestant work ethic" and capitalist society), the notion that many (even today) hold that women should be primarily caregivers in the home is ideological (along with its cousin, the belief that emotional or even reproductive labour does not truly count as labour because it is not valorized). These ideologies come about due to the economic system that underlies them, capitalism. Under different economic systems, or even different time periods, these ideologies are not present, or they are in a different form (see the last paragraph of my comment).