Well there is nothing inherently bad about shrinking or smaller populations, they do pose significant challenges to the current social and economic models, which are based on growth and large working age populations.

Lower Workforce participation means people working more For Less personal reward. It also requires a transition away from using that too fund governmental function. Most governments use GDP growth and a higher future tax base to negate the fact that spend more than they receive.

In terms of impact to real people, this means adjusting to life with less material wealth. This doesn't just mean fewer trinkets, but also cuts to social Healthcare and welfare spending