The world has gotten a lot more understanding, but all up until the 1980s or so, virtually the whole world had mob mentality, hit kids in school, had many more taboos etc... than now.
Reading up on a few philosophies of the past, I'm puzzled as to how our world didn't progress sooner. In Greece, they had democratic societies B.C.E. In historical Scandinavia and parts of Eastern Europe, women were given a higher place in society. In the ancient Greece and Middle East, they had remarkable mathematicians. Even the Age Of Enlightenment sparked a more understanding mentality from the public of Western Europe.
How is it that it took us all up until the late 1800s/early 1900s to start developing technology? How is it that it took us all up until now (in some places of the world) to become a lot more understanding to social issues and minimize taboos, if throughout history, there were many examples of societies who were, at times, more progressive than parts of our modern world?
There are a few issues with your premise that I hope I can explain well enough:
You are assuming your worldview is best by conflating "progressive" with specific morals When we talk about "progressive" politics, we must remember that it is a relative term, the opposite of "conservative." Neither completely encapsulates one person's views, nor is one inherently right. You appear to be associating your own perspectives on whats right and best with progressiveness. Modern usage does often conflate specific values with the word "progressive." But we must remember that those values are only called "progressive" in that to attain them we must progress from our current state. If we already had them, they would be "conservative." When we use "progressive" to refer to defined morals (minimized taboos, etc.), we can't then go back and use it in the sense of "advanced" or "developed" Greece having democracy doesn't make them more progressive, it just makes them closer to what you believe is right. They hadn't progressed further than everyone else, they were just different. But because we like to think their democracy gave birth to our own system, we like to the call them "progressive." (That's a bit of a mess, I hope it makes sense.)
You assume a natural progression: Even if we were to agree on a certain absolute pinnacle of human society, an ideal Eden or Utopia, history is not inevitably marching towards it. We're not aboard some invisible 5th dimensional train that carries humanity towards perfection, nor is this a game of Civilization, where we need to unlock "Voting Rights for All Races" before we can research "Civil Rights Act" with our accumulation of arbitrary points. Historians don't construct predictive models for history, nor do we believe there are certain ways history "should" go, as if there was some natural inclination towards any path. You're assuming there's a certain way history "should" be and asking why it isn't like that. But history is the way it is, and we can only give you possible reasons why certain things have happened. We can tell you why bananas are yellow, but we can't tell you why they didn't evolve to be red. We especially can't tell you why something didn't happen when there are no reasons it should have to begin with. Make sense?
I think the best reply to your question might just be the popular catchphrase from the Fallout series of post-apocalyptic video games:
War. War never changes.
The more you study history, the more you find that people have never been all that different. We don't burn witches anymore not because we've developed morally, but because belief in witches has declined. If you honestly thought that someone in your town was infecting children with various diseases and ruining your crops, you might set the police on them and have yourself a little witch hunt. We might have unseen levels of racial integration and religious freedom, but we also have unseen levels of economic inequality. War, oppression, and personal conflict have existed wherever you look. But while I can read Maya inscriptions of warfare and see wars of the present in them I can also look at a Maya vase and see a Saturday morning cartoon in the antics of its characters. I can see modern economic issues in those of ancient Rome, but I can also see Ferris Bueller's Day Off in the Roman satirical novel Satyricon. We have no evidence to say that people of the past were more or less moral than any of us today.
(Technology is another thing. It should be no surprise that you need the Model T before you get the Ferrari. But of course you also need the carbon fiber, which is practically an entirely new industry that didn't exist 200 years ago. You can find more about this topic in our FAQ or by searching.)
TL;DR There are two definitions of progressive: "a certain set of modern political and moral beliefs", and "advanced, forward-thinking, developed." We cannot conflate these two meanings to suggest that modern Western "progressive" politics are universally more advanced. History does not have a track on which it "should" run; we can only give you answers why things did happen. People are people.