You bring up assets. I think per-industrial economies the majority of couples have no ability to gain modern assets. Things like land and infrastructure was locked down. Unless you wanted to try to take stuff by force you were SOL. So only thing you could do is have a lot of children whose value was performing labor. Only encouraged by a high childhood mortality rate.

Switch to an industrial society. Having children to do raw physical labor competes directly with tractors and a backhoes. But you can acquire other assets and put more resources in upscaling children through education. And wage work means you can send wives and daughters out to make money.

I think it usually takes a society one or two generations to figure that out and act accordingly.

Adding a thing I harp on. Malthusian limits traditionally is thought to apply to just food and disease. But you can extended that to an industrial wage based economy and the resource restrictions still apply just not to food and disease. Industrialization probably results in structural population overshoot.