I believe there is a misunderstanding about the Soviet Union's industry, its system of mobilization, and its form of warfare during a state of war. These elements can easily explain why the Soviet Union WOULD NOT sign any form of peace agreement with Germany.
A) The Soviet Union was a relatively industrialized nation that also happened to be socialist. Its Socialist nature allowed for its industry to be nationalized without too much difficulty early in the war and to be able to put a emphasis on military goods rather than consumer goods. However, due to the vast gains made by the Germans (to be explained in section C) they had to evacuate a vast majority of their economy to the east in order to keep it operational. This evacuation sucked the wind out of the USSR's lungs for all of 1941 and the beginning of 1942 but would start showing results by 1943 with a relatively unmolested industrial capacity. This action allowed for the Soviet Union to continue operating at a decent scale and with a emphasis on military goods rather than consumer goods.
B) The Soviet Union relied on a system of mobilization in order to raise an army to fight foreign powers. This is a factor drastically overlooked when comparing the actions of Germany to those of the Netherlands, Poland, and Norway which expected no real confrontation with Germany. Nations would see mobilization as further expenditure with no real benefit during peace. Therefore, it makes more sense for the Soviets to keep a professional active army and a massive reserve army in order to beat off foreign powers who would take time in order to invade the Soviet Union. The main expectation being that the enemy wouldn't quickly overrun the forward positions with overwhelming forces but would rather be allowed to push slowly while being heavily harassed by active Soviet forces while the Soviets gathered a force that was stronger in numbers and equipment to overwhelm the enemy.
C) The Soviet Union as a result of its previous two features would find protracted warfare heavily in its favor as they would be able to eventually overwhelm the enemy due to manpower, industry, and territory. However, the Soviet Union would require time in order to properly mobilize for the purpose of maintaining this style of warfare but only saw failure after failure in 1941. Moreover, it was unlikely that the German Military would've been stopped even with this strategy due to the disparity of troop quality, supply, organization, and tactics during 1941. The expectation of the Soviets was actually something similar to this though, and the Soviet Army simply retreated further into the Soviet Union as a result. This is one of the reasons Order 227 was issued and why towards the end of 1942 that we see a sudden seize in German advances across the entire front line. This quote from the Former OKH Chief of Staff, Kurt Zeitzler, in June 1942 when describing readiness of Axis units for Case Blue shows the strategy even proving effective to both Soviet and German High Commands; "Military objectives must always correspond to the forces and other means available for their attainment...we lack the materials, manpower, and quality(1) required..." It also partially explains the failures of Case Blue and why the Battle of Stalingrad was a massive German failure.
I could try to flush this explanation for why the Soviet Union would not surrender with more features, explanations, and other factors but its apparent that the Soviets expected a protracted war to which the Germans were kind enough to provide. The results of all these factors establish a solid argument that the Soviets simply wouldn't sign a peace agreement for doing badly in the first 2 years of a war they expected to suffer in anyways.
(1) - quality referring to the experience of fielded units
A) The Soviet Union was a relatively industrialized nation that also happened to be socialist. Its Socialist nature allowed for its industry to be nationalized without too much difficulty early in the war and to be able to put a emphasis on military goods rather than consumer goods. However, due to the vast gains made by the Germans (to be explained in section C) they had to evacuate a vast majority of their economy to the east in order to keep it operational. This evacuation sucked the wind out of the USSR's lungs for all of 1941 and the beginning of 1942 but would start showing results by 1943 with a relatively unmolested industrial capacity. This action allowed for the Soviet Union to continue operating at a decent scale and with a emphasis on military goods rather than consumer goods.
B) The Soviet Union relied on a system of mobilization in order to raise an army to fight foreign powers. This is a factor drastically overlooked when comparing the actions of Germany to those of the Netherlands, Poland, and Norway which expected no real confrontation with Germany. Nations would see mobilization as further expenditure with no real benefit during peace. Therefore, it makes more sense for the Soviets to keep a professional active army and a massive reserve army in order to beat off foreign powers who would take time in order to invade the Soviet Union. The main expectation being that the enemy wouldn't quickly overrun the forward positions with overwhelming forces but would rather be allowed to push slowly while being heavily harassed by active Soviet forces while the Soviets gathered a force that was stronger in numbers and equipment to overwhelm the enemy.
C) The Soviet Union as a result of its previous two features would find protracted warfare heavily in its favor as they would be able to eventually overwhelm the enemy due to manpower, industry, and territory. However, the Soviet Union would require time in order to properly mobilize for the purpose of maintaining this style of warfare but only saw failure after failure in 1941. Moreover, it was unlikely that the German Military would've been stopped even with this strategy due to the disparity of troop quality, supply, organization, and tactics during 1941. The expectation of the Soviets was actually something similar to this though, and the Soviet Army simply retreated further into the Soviet Union as a result. This is one of the reasons Order 227 was issued and why towards the end of 1942 that we see a sudden seize in German advances across the entire front line. This quote from the Former OKH Chief of Staff, Kurt Zeitzler, in June 1942 when describing readiness of Axis units for Case Blue shows the strategy even proving effective to both Soviet and German High Commands; "Military objectives must always correspond to the forces and other means available for their attainment...we lack the materials, manpower, and quality(1) required..." It also partially explains the failures of Case Blue and why the Battle of Stalingrad was a massive German failure.
I could try to flush this explanation for why the Soviet Union would not surrender with more features, explanations, and other factors but its apparent that the Soviets expected a protracted war to which the Germans were kind enough to provide. The results of all these factors establish a solid argument that the Soviets simply wouldn't sign a peace agreement for doing badly in the first 2 years of a war they expected to suffer in anyways.
(1) - quality referring to the experience of fielded units