Except that consumption is exactly what capitalism drives - particularly manufacturing, where a relatively fixed amount of capital (factories & machinery) can drive higher overall profits if more products are made for people to consume - even if those people don't actually need the products.
Apparently (I can't find the source for this, but it stuck in my mind), faced with a glut of production after WW2, the US could either consume more, or work less. The choice was made to consume more, not least because the industrialists could cream off a larger slice of the pie that way.
Having children still fuels consumption though. The difference is what is being consumed vs if that consumption spending were not spent on children. I think you are mixing up the colloquial definition of consumption of ie random plastic crap with the economic definition that is very broad and includes things like paying teachers.
Similarly regarding manufacturing and production glute, if the hard capital is fixed then so too typically is the hard production (not the case for many kinds of capital but it is for manufacturing) or at least capped. Just like with consumption, it’s a problem of what portion of capital is being expended on increasing production of things for children (housing, schools, kid stuff) or not. In both cases this is ultimately driven by the supply and demand stemming from parents themselves. But I don’t think there is a feedback loop because capitalism does not itself care whether capital goes to kids or not, only whether there is enough demand for capital expenditure to be profitable.
Apparently (I can't find the source for this, but it stuck in my mind), faced with a glut of production after WW2, the US could either consume more, or work less. The choice was made to consume more, not least because the industrialists could cream off a larger slice of the pie that way.