The idea of "Red human waves" was introduced in the various self-serving, exculpatory memoirs produced by German officers after the Second World War, and was of course reinforced by such films as Enemy at the Gates. These memoirs were typically attempts by German officers to excuse their defeat with cliches such as "well, they only beat us because they vastly outnumbered us" (why go to war with them, then?), and were usually mixed in with racialist ideas about a faceless, unimaginative Slav horde coming to destroy all the West held dear. What with the Soviets becoming the enemy during the Cold War and the difficulty of accessing Soviet sources, these became the accepted accounts by many for much of the rest of the 20th century.

In fact, from 1942 the Red Army had an exceptionally well-developed offensive doctrine. Deep Battle, originally developed in the 1920s by Marshal Mikhail Tukhachevsky but largely abandoned after his conviction and execution during the Purges, was resurrected. Deep Battle involved levering the Soviet Union's immense advantages in population and industry to launch broad-front attacks with heavy firepower and numerical superiority to create many small encirclement and destabilise the front line. This would be followed by reserve forces pushing through to create larger encirclements around enemy reserves in the operational depths. We can see this approach begun in the Soviet winter counteroffensives of 1941-42, refined during Operations Uranus, Little Saturn, Star and Gallop in 1942-3, and reaching its zenith in Operation Bagration, the Lvov-Sandomierz offensive, and the Jiassy-Kishinev operation of 1944.

There are some understandable reasons why the Germans would interpret Soviet attacks as "human waves" (beyond the racism, of course): most military historians will accept that even by late 1944 German tactical staffs were consistently superior to their Allied counterparts, though conversely Allied operational and strategic thinking was consistently better. This combined with the fact that the relentless, vast Soviet offensives must have started to blur together for beleaguered German soldiers must have created the impression that they were facing a ceaseless wave of men: it is much easier to know that you are taking part in a discrete operation when your side is launching the offensive.

To summarise, Soviet tactical thinking may have been inferior to the Germans'; I am not sufficiently well-read to comment on that. This may have some influence on the myth of the "Red human waves". However, at the operational and strategic level the Soviet Union consistently outperformed Germany and the offensives from late 1942 through to 1945 are entirely admirable pieces of military thinking. The idea that the Soviets only won thanks to brute force and superior numbers is almost entirely the product of German officers writing one-sided histories after the war.

Sources:

Antony Beevor, Berlin: The Downfall 1945

Antony Beevor, Stalingrad

Lloyd Clark, Kursk: The Greatest Battle

Robert Kirchubel, Atlas of the Eastern Front

Robert Kirchubel, Operation Barbarossa: The German Invasion of Soviet Russia

Anthony Tucker-Jones, Stalin's Revenge: Operation Bagration and the Annihilation of Army Group Centre