In Russia, in particular, the nostalgia is strong because of national pride. Russia's early history was that of an Asian hick backwater. With Peter the Great, they became a European power, albeit a minor one. With Catherine, they became prominent and rose to be a major force in the never-ending series of European wars. But they lost quite a few of them.
Then, after World War II, they were a superpower -- feared and hated. The nostalgia leads to a "but at least" problem. "Well, we had to wait in line for rotten bread, but at least we didn't have to worry about paying for the doctor." The real problems that Russia suffers from now are compared against a sanitized version of the past. But the truth is, it's really more about national pride. They don't have it now, and they wish they did.
Actually, Kieven Russ and the surviving principalities of Novograd, Moscovwy, Pskov and Vladimer (after the state was dismembered by the Mongols, Poles, Lithuanians, Teutonics and Swedes) were all very much in Europe. Only with Novograd's colonies into Siberia, which became Moscowy's after Novograd was conquered, did the Russ venture into Asia.
As for a backwater, hardly. Up until the Mongol invasions, they were one of the most powerful states in Europe, while England, France, Spain, Germany and Italy were hundreds of small baronies fighting for power.
Actually, they were already a European power before Peter, who made them into a major power with his defeat of the Swedes and Poles and Turks. Catherin even conquered Berlin before her death and her idjit son (who hated her) Peter III gave it all back to Fredrick (at that time) the Not-So-Great.