Then what was Article I section 10 of the constitution all about?
Levying property taxes on real estate and slaves, in the same manner as the states did, by collecting them form the owners of such property same as is done today in most states/counties.
It is a signal advantage of taxes on articles of consumption, that they contain in their own nature a security against excess. They prescribe their own limit; which cannot be exceeded without defeating the end proposed, that is, an extension of the revenue. ... Impositions of this kind usually fall under the denomination of indirect taxes, and must for a long time constitute the chief part of the revenue raised in this country.
Those of the direct kind, which principally relate to land and buildings, may admit of a rule of apportionment. Either the value of land, or the number of the people, may serve as a standard. The state of agriculture and the populousness of a country have been considered as nearly connected with each other. And, as a rule, for the purpose intended, numbers, in the view of simplicity and certainty, are entitled to a preference.
As was also pointed out by the first Supreme Court, where 3 of four of the judges ruling on the case were Delegates to the Constitututional Convention:
Hylton v. United States(1796), 3 U.S. 171
Check out he hyperlinks I have provided, they go to the transcripts of the early papers and Debates in regard to the Constitution and our early government. There is a wealth of information there. There seems to be alot of myth and misinformation floating around as to what the Constitution really is about. I highly suggest the study it is eye opening once one get into what the founder really had to say and did back then.