It's mostly a matter of definition. Was the system in which slaveholders and segregationists lived a "racist system"? If you think racism is defined as being about individual attitudes, then the term makes little sense. And it's certainly true that we have been gradually mitigating these systems of oppression, so their consequences are not what they once were. Of course, this suggests that further progress might also be possible, should we find out that problems still exist (as with police brutality and biases in the criminal justice system). Both perspectives are valid and both should be taught for a full understanding of where we might be standing now.