Certainly the Soviets would have a harder time fighting the Germans alone (and I'm going to assume Britain is out of the war by 1942/43), but the Soviets had a lot of really significant advantages. For one thing, funny enough, Soviet industrial production of all war equipment (barring ships) was superior to that of the Germans for every year of the war, including 1942, when the Soviet heartland was under occupation. The German system of production, meanwhile, was very inefficient, with a wide variety of weapons being produced in small numbers rather than a few weapons being produced en masse
The Soviets were able to focus their production on different items then the Germans did. The Soviets fighter air force was woefully inadequate to the German one but the Soviets fought with air superiority. The Soviets could focus on building tanks because they didn't need to build any trucks and trains. The Soviets could have 2 or 3 times the indirect fire heavy artillery because they didn't need to defend against a massive strategic bombing campaign.
I will readily grant you that German tank production was horribly mismanaged but beyond that there aren't many obvious deficiencies in German production. You just need to realize that Germany and Russia needed different kinds of production. Rifles would be a pretty good example, the Soviets massively outproduced the Germans in rifles but it's not like the Germans were ever suffering from a shortage of those at the front (until the very end). Why? Well the German rifle stocks weren't overrun and destroyed in '41 and '42 so they didn't need new ones.
Soviet production was certainly focused on different areas thanks to Lend Lease and the strategic bombing of Germany, yet both of these factors are overblown considering the fact that the Soviets
still outproduced the Germans in nearly every aspect from 1940 to 1942, while Lend Lease and serious strategic bombing only had significant effects by around 1944.
To go into a bit more detail with regards to Lend Lease, the Soviets mainly received three main things from the Americans: locomotives, food, and jeeps/trucks. Locomotives are often brought up as a major contribution, but they actually were largely unnecessary; as a result of the German advance, most of the extended Soviet rail lines were occupied, yet most of the locomotives the Soviets had before the war were safely evacuated along with other industrial materials. So the Soviets were sitting on a pile of trains that they couldn't use, in amounts that dwarfed what the Americans sent over, and by the time the American locomotives were at all useful the Germans were basically beaten anyway. Food was useful, but the food supplied was insufficient to feed the Red Army for even a few months, and thus was a minor benefit at best. The arrival of jeeps and trucks was the most helpful part of Lend Lease, but they almost all arrived after 1944, so that doesn't explain the superiority of Soviet production before that time.
Anyhow, in terms of the air war, the Soviets still outproduced the Germans, with their main problems being (A) inferior plane designs and (B) a lack of experienced pilots. The first problem was largely solved after 1943 when the Yak-9 and Yak-3 became the common Soviet fighter planes, while the second became less of an issue over the course of the war as Soviet pilots became more experienced. By the end of the war, Soviet fighters were generally superior to those fielded by the Luftwaffe, so even the air war would be won by the Soviets.