Below Replacement Fertility Isn't Necessarily A Bad Thing:
As long as a healthy eugenic segment of the White populace has a high fertility rate (at least replacement) then low fertility rates can be a useful tool to consolidate the race and emerge more eugenic, shrinking the more dysgenic portion of the race.

Given the above 2018 TFR chart, Whites actually have a good spread of TFR, with only the highest point (presumably most eugenic) above replacement rate (when ignoring the lowest point, which should be reduced below replacement).

The only corrective action here is reducing Nonwhite fertility below White fertility in each respective bracket, well below replacement.
We are already seeing this rapid correction take place.

It would be ideal to think of the world-wide fertility collapse to 0, as a modern Noah's flood, indiscriminately removing all dysgenic Whites, Non-whites, etc, without violence, death nor pain; just low births.

All that needs to occur is the best Whites have exceptional fertility rates.