JWK
Point is there are direct taxes, and indirect taxes. Indirect federal taxes (such as taxes on wages, tariff, excise taxes on liquor) have never been required to be apportioned by population in the present constitution.
Taxes on property were required to be apportioned by population before the 16th Amendment, and were not required to be apportioned by population after the 16th amendment. Most US federal taxes are not direct taxes.