At the time of the dinosaur, our ancestor was essentially a rodent. "We" have evolved greatly since then but it raises an interesting question: how are we to judge that ancestor's morality?
And while that's a dramatic example, I think the same general complications apply in any attempt to judge generations from centuries earlier. If climate change does irreparable harm to coastlines and their cities, makes species of plants and animals extinct and forces political turmoil and violence with climate refugees, do you really think that your descendants aren't going to be horrified that you took joy rides driving up the coast or that you flew to other continents just to play tourist?
It's the rare individual who constructs their own morality separate from what they see around them. We tend to share language and worldview with the people we consider us.
If we're making progress, we will be aghast at the technology - and worldview and morality and behavior - of our ancestors. It doesn't mean we can't acknowledge when they did things that changed the world - and call out the the things they did that were so casually brutal.
And then rather than decry the treatment of others from that period, champion policies that narrow the gaps between "others" and average Americans. We can't judge a rodent's behavior from the time of the dinosaurs but we also don't have to accept the consequences of that behavior as if we're helpless to change history. We're no longer the rats in the maze; we're the ones in the lab coat who can now change the maze.