The problem you describe as "temporary" implies that once your children are grown, they don't have further children that will use more resources.

A worker in a growing population can somehow support 4 children and 2 parents (6 dependents) yet supporting only 2 parents and no children (2 dependents) is a problem?

So no, it's not "temporary". It's a pyramid that eventually grows such that the foundation must crumble from the weight of everyone above.