Most certainly, but that also has to be balanced by the fact that without Stalin's ruthless five year plans forcing through industrialisation, the USSR wouldn't have been in any sort of position to equip and maintain an army capable of halting the Germans at the gates of Moscow, Leningrad and Stalingrad....
Without Lend-Lease though he never would have been able to pull that off. The Western Allies provided him with the machine tools needed to get the industry that had to be evacuated over the Urals up and running. Also, Stalin was able to maintain a mostly motorized force without having to use industry to build trucks. The bulk of the Soviet logistical motorization was provided by the United States allowing the Soviets to focus on making the T-34 and more artillery than you can imagine.
During the Cold War the roll of Lend Lease was downplayed by the Soviets for obvious political reasons. Over the last 10 years though more and more old Soviet archive files have revealed just how significant this lifeline was to keeping the Soviets from folding altogether. The first shipments of the First Moscow Protocol sent to the Soviets on the dangerous run from England to Archangel were not large, but just enough to keep the Soviet Union in the war which was of vital importance to Churchill and Roosevelt. Now I do not agree that if the Soviet Union had surrendered that the Allies would have lost the war, but it would have taken significantly longer to win and likely would have resulted in a tactical nuclear war by the Allies in Europe.