To be fair competitions in all sports allow access to every country. It’s always been that small countries play - it’s just that so many European countries are allowed in the World Cup
They can and other confederations have prelims, AFC pits. If anything, integrating the Nations League into the qualification process enhances the prospects of lower tier nation. As England found out, relegation to Tier 2 in the nations league had 0 consequence so for the Nations League to stand up as a meaningful competition, maintaining that Top 16 rank has got to matter.
One proposed format is:
1-16 ranked teams qualify automatically
17-32 are then in a playoff style league/competition for 4 playoff qualifiers
The overall product of World Cup qualification is dross. Anyone that follows England turn up to get the points or an away day to somewhere new. The gap of opponents is too high and it’s undermining the international game because there’s widespread apathy when international windows come about.
Generally, people like the Nations League so it makes sense to broaden that and frankly, it must have much stronger commercial opportunities.