Also, think of how many backsteps things have probably taken due to the massive, galactic wars that go on. Think of the crusades, technology in the Middle East was FLOURISHING at the time of the crusades...and perhaps that single collection of events set Middle Eastern technology and culture back...how far? Think of that on a galactic scale, multiple Jedi-Sith Wars, Sith-Republic Wars, Republic-Empire Wars...I'm sure that's gotta cause things to at least stagnate if not regress.
This is a misconception; during war, technology leaps forwards to accommodate for the need to outdo the enemy. In Earth's history, the greatest technological advances were based off militarist needs and demands. The Internet itself was built in order for the army to share information, even after a nuclear attack.
I think the thing you have to realise is that the tech of eps I-VI are only a sliver of what is actually present in the entire SW universe. The reason things look so much more advanced in the Old Republic is because that's what the player wants, they want to see all the galaxy has to offer, where as the movies were telling a story.
The Old Republic was a period of expansionism and galactic exploration, there is a techno-boom, stuff is new and its flashy, people were explorers or settlers and needed to buy the best survival gear to carve their niche in a foreign world.
In the Rise of the Empire era, that stuff would be mundane and "old-world", there was no more exploration and people lived lives much like they do on Earth, where you don't need the gigantic battle stations, and lasers, and survival gear, and such.
