The increase in global population is not necessarily exponential. A lot of it can be explained by increases in life expectancy, and those increases seem to have - for now - a relatively fixed limit. Longer life expectancy does not increase the number of children each person has (for the most part, leaving ageing rock stars to one side).

Greater wealth seems to also have discourage people from having children if the birth rates in wester countries are any indication.

I think we can do more to tackle the specific problems you mention through regulation and better policy, whereas a falling global population on its own would do little or nothing to combat them.