Excellent point!
If you aren't qualified to vote in your state elections because of state voting laws which prohibit you from voting for reasons which aren't protected by the Constitution, then you aren't qualified to vote in federal elections either.
Probably the only reason that state voting laws are being challenged for federal elections is because of a combination dirty politics as a consequence of the Democratic & RINO agenda to unconstitutionally centralize government power in DC, and Constitution-ignorant voters.
Regarding Constitution-ignorant voters, note that the reason that people would likely get upset about being proibited from voting in federal elections is because they probably don't understand the constitutionally limited powers of the federal government. After all, in times of peace, practically the only intrastate commerce-related issue that Congress has the constitutional authority to regulate, tax and spend for is the postal service (1.8.7).
And note that not only did most citizens evidently did not initially pay for postal services as evidenced by the fact that postage stamps were not issued until about the mid-19th century (corrections welcome), but consider the following. Thomas Jefferson had noted that, initially, only the rich paid taxes to make the federal government operate.
"The rich alone use imported articles, and on these alone the whole taxes of the General Government are levied (emphasis added). … Our revenues liberated by the discharge of the public debt, and its surplus applied to canals, roads, schools, etc., the farmer will see his government supported, his children educated, and the face of his country made a paradise by the contributions of the rich alone, without his being called on to spend a cent from his earnings." --Thomas Jefferson to Thaddeus Kosciusko, 1811.
And since only the rich used to pay taxes, with the exception of state and federal military-related training, I wonder if the federal government was nothing more than something to gossip about to pass a little free time for many pioneering voters.
Finally, as a side note to congressional elections, if the federal government was still in compliance with its Section 8-limited powers as it should be, voters would likely have to guess when asked who the current president is.
Do you happen to know if “direct taxes” authorized by the Constitution were ever levied?