The Old Republic era went from about 25000 BBY to around 1000 BBY. KotOR didn't invent the era. Though they did change it a bit as well... Now, if you're talking about the actual KotOR era, it's technically not the KotOR era as it is 300 years after the games...
300 years is a long time to still hate a group of people. Unless you still hate Germans, Japanese, and Itallians, it took significantly less time for a real world example of people getting over past differences.
Technology... Well you do have technological plateaus. Cars still function pretty much the same way they have for a hundred years. Just faster and easier to operate. Not to mention when you have multiple cultures mixing, together, things may move fast, or just stagnate. Not to mention you have a Galactic government, so I'm pretty sure you have a galactic safety requirements comittee... Then there's the Galactic EPA... Or the Galactic Transportation Safety Administration, Galactic Historical Preservation Society?
At any rate, The reason things may not have changed all that much could simply be that they had no reason to change. I mean they already have flying cars, and faster than light travel... How much further do they need to go?
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson