Desertion in the face of the enemy has been (at least theoretically) punishable by death in almost every army since 1200 BC.
For instance: 15,000 Wehrmacht soldiers were executed for desertion in WW II.
The Germans only came near the Volga at Stalingrad, nowhere else.
The Soviet Union won every strategic series of battles after the 1941 Battle of Moscow, at Stalingrad, Kursk and later in Operation Bagration, pushing the Germans all the way back to Berlin. Hardly ill equipped and ill trained soldiers "holding out at all".
You can't really judge a 1200 day campaign by the first 200 days.
"The Unknown War" by Harrison E. Salisbury is a nice intro to Operation Barbarossa, not very accurate but light reading with lots of pictures.

Then there's the German side of the story:

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“…The Commissar was the driving force of the Red Army, ruling with cunning and cold-bloodedness. Commissars came mostly from the working class, were almost without exceptions city people, brave, intelligent, and unscrupulous. But they also took care of the troops. The example set by commissars is largely responsible for the tenacious resistance of the Russian solder, even in hopeless situations. It is not wholly true that the German commissar order, directing that upon capture commissars be turned over to the SD for “special treatment”, that is execution, was solely responsible for inciting the commissars to bitter last-ditch resistance; the impetus much rather was fanaticism together with soldierly qualities, and probably also the feeling of responsibility for the victory of the Soviet Union. Then too, in innumerable other cases dogged perseverance even under hopeless conditions was to be credited to the soldierly conduct of the commissars. For instance, in September 1941, long after the castle of Posyolok Taytsy (south of Leningrad) had been taken, and strong German troop units had been drawn up in the castle park, German tanks passing near the park wall with open hatches drew single rounds of rifle fire from close range. The shots were aimed at the unprotected tank commanders who were looking out of the turrets. Not until three Germans had been killed by bullets through the head did the passing tank unit realize that the shots were coming from a narrow trench close under the park wall ten yards away. The tanks then returned the fire, whereupon all thirteen occupants of the trench met death. They were the officers of a Russian regimental headquarters, grouped about their commissar who fell with his rifle cocked and aimed. After the German divisions broke out of the Luga bridgeheads in August 1941, the commander of a task force inspected several Russian tanks which had been knocked out two hours earlier near a church. A large number of men were looking on. Suddenly, the turret of one of knocked out tanks began to revolve and fire. The tank had to be blown up . It turned out that among the crew, which had been assumed dead, there was a commissar who had merely been unconscious. When he revived and saw many German solders around him he opened fire. When in April 1942 the Germans took a strong position along the Osuga (southwest of Rzhev), they continued to receive fire from one lone barricaded bunker. All demands for surrender were in vain. When an attempt was made to shoot through the embrasure with a rifle, the Red soldier grabbed it and fired the last three shots. Two of the bullets wounded German soldiers. The commissar, who was defending the bunker alone in the midst of his dead comrades, then shot himself with the third. The commissars found special support among the women who served within the framework of the Soviet Army. Russian women served in all-female units with the so-called partisan bands, individually as gunners in the artillery, as spies dropped by parachute, as medical corps aides with the fighting troops, and n the rear in the auxiliary services. They were political fanatics, filled with hate for every opponent, cruel, and incorruptible. The women were enthusiastic communists-and dangerous. It was also not unusual for women to fight in the front lines. Thus, uniformed women took part in the final breakout struggle at Sevastopol in 1942; medical corps women in 1941 defended the last positions of Leningrad with pistols and hand grenades until they fell in the battle. In the fighting along the middle Donets in February 1943, a Russian tank was apparently rendered immobile by a direct hit. When German tanks approached, it suddenly reopened fire and attempted to break out. A second direct hit again brought it to a standstill, but in spite of its hopeless position it defended itself while a tank-killer team advanced on it. Finally it burst into flame from a demolition charge and only then did the turret hatch open. A woman in tanker uniform climbed out. She was the wife and co-fighter of a tank company commander who, killed by the first hit, lay beside her in the turret. So far as Red soldiers were concerned, women in uniform were superiors or comrades to whom respect was paid. The four elements which determine the nature of Russian warfare-the higher command, the troops, the commissar, and the Russian terrain-fitted together in such a way that their combination was responsible for good performance and great successes…”

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GeneralOberst Erhard Rauss, Commander, Fourth and Third Panzer Armies, Russian Combat Methods in World War II.