True, in general. However, in at least 5 states blacks had the legal right to vote in 1787.
What Taney did was to go back in history and retroactively exclude those, admittedly few in number, voters from "the People" who established the Constitution. It was not an exercise of states' rights, it was a denial of those rights. He said that regardless of what individual states did, Africans were not and never could become citizens of the United States.
This was not only morally wrong, it was historically inaccurate. When Taney didn't like the facts, he just ignored them.
He said the courts did not have the power to make them citizens of the United States. And he was right. It took a constitutional amendment.
You're shooting the messenger.