VNL format

16 national teams will compete in the inaugural edition of the tournament; 12 core teams, which are always qualified, and 4 challenger teams, which can face relegation.
The relegation will consider the four challenger teams and the last ranked challenger team will be excluded from next edition. The winners of the Challenger Cup would qualify for next edition as a challenger team.

This year it will be 4th edition of VNL and we have the same challenger teams since beginning.
The question is, why none of this challenger teams got promoted to core teams?
Belgium has ended VNL on 13th place in 2018, on 7th place in 2019 and on 9th place in 2021.
Dominican Republic on 14th, 8th, 6th.
Poland on 9th, 5th, 11th.

Don't you think that Poland and Belgium deserve to be promoted to core teams?