I don't think this statement stands up to historical review. The ratification of the Seventeenth Amendment in 1913 immediately and permanently altered the balance of power between the states and the federal government. Almost immediately after the passage of the amendment, there was a rapid growth in the power of the national government, especially at the expense of the powers of the states.
While the Founders were careful to guard against the “excesses of democracy, ” the Seventeenth Amendment embodied a notion that the cure for the ills of democracy was more democracy. Clearly, then, the passage of the Seventeenth Amendment was a direct assault on Our Federalism, because, as the Founders noted, the idea of a state having a direct voice in the national government was a key check to the power of the national government. Without the careful check in place, the national government began to legislate in areas traditionally only available to the states.
For instance, following the adoption of the amendment in 1913, Congress quickly passed the Child Labor Act of 1916 and the Child Labor Tax Act of 1919. While this legislation might have been meritorious, such legislation was always understood to be beyond the power of the national government, and its passage was a direct assault on the states as states.
Although the New Deal legislation was probably the high-water mark on the assault on the states by the national government, the clear trend following the ratification of the Seventeenth Amendment was that Congress was given an essentially blank check to legislate according to any perceived problem without any consideration of the states as separate entities.
This problem remains today in a variety of areas, but perhaps most conspicuous is Congress’s increasing legislation in criminal law, a sphere that historically has always been left to the states. Indeed, even following the ratification of the Fourteenth Amendment, in which Congress was given power to enforce equal protection and due process requirements, the Supreme Court in U.S. v. Cruikshank still held that Congress had no power to make general criminal law, striking down an indictment against several whites accused of killing a group of black men.
Despite recent trends by the Rehnquist Court to judicially impose requirements of federalism, the judiciary was not intended by the Founders to act as a check on the power of the national government vis-à-vis the states, and the weakness in attempting to extend the power of the judiciary that far becomes clear: the court simply cannot declare the vast number of laws intruding on the powers of the states unconstitutional and still retain any aura of legitimacy. In a nominally republican society, an unelected judiciary simply cannot, on an extended basis, continue to invalidate legislation passed by a democratically elected Congress; thus, the check on the power of the national government must come from the legislature itself. The Seventeenth Amendment removed this check. AS to your comment about the Senate not necessarily being composed of the wealthy any powerful, I note only that it wasn't called "the millionaire's club" for no reason.