In decline for now.

Human society jumped by billions in a hundred years.

It can stabilize just as fast, or faster.

The issues simply need ti be resolved.

Changing how women and young people in general live their lives is all that is needed. Better pay while people are young, cheaper housing to feel secure, secure work positions.

Of course a woman does not want to have kids when she has to start a career and build it until early thirties.

Of course young couples do not want more kids, when housing is exoensive, as are living expenses.

People in poor countries do not have more kids, people in less educated places have less kids. You start to think "maybe I do not want to have kids if they cannot live like I do".