It was working perfectly until 1920 when we passed the 19th amendment allowing women to vote.
No, it wasn't working perfectly. The 14th Amendment reversed the relationship of the States and the Federal government. The 16th Amendment undid the restrictions on the taxing power put in place by the Framers. The 17th Amendment undid the original plan of government, converting the Senate into a House with six year terms, and leaving no Federal representation of the State legislatures. Even before the 16th Amendment, the Lincoln administration gave us greenbacks, an unapportioned income tax, and the Internal Revenue Bureau (now Service) to enforce the then-unconstitutional tax.
The American People needed a reason to be vested in the government. So that's why we passed all those amendments. They were flawed, yes.