Population growth has dropped below the replacement-level fertility rate in many countries. Does this mean earth no longer has a problem with population numbers?

It does not

Explanation:

Even though population growth has dropped below the replacement-level fertility rate in a lot of countries, it doesn't change the fact that children are still being born.

Every child that is born has the potential to increase the population by more than 1 when they become parents so human population will still grow.

Add that to the high population growth rate of less developed countries and it is still evident that earth has a population problem.