That is patently untrue. Soviet Union led the world in modern combat aircraft as well as tank development and production for much of 1930s. The Polikarpov I-16 was the first fully modern (stress skin monocoque, cantilever monoplane wings, retractable landing gear, nearly or fully enclosed cockpit) fighter to be developed and to be mass produced in the world. Way before T-34 Soviet tanks such as BT-7 were already fully competitive with the best in the world.
This is very debatable. the I-16 and T34 had no radios, egronomics was bad (but acceptable to Russian farm boys), The I-16 have very simple controls surfaces - nothing of fancy ailerons, manual landing gears, artificial horizons were counter intuitive. The BT had their fare share of issues too, very prone to break down, insufficient armor to resist machine gun fire.. There is a reason why the T-26 soldier on, while the BT did not. They are advanced in their own ways, but hardly world beating.
The fact that Germany enjoyed superiority in modern combat aircraft does not imply Soviet Union was comprehensively behind. The nature of military aircraft life cycle is such that competitors trade advantages back and forth. When a competitive power first mass deploy a new fighter, that fighter would usually enjoy significant superiority over those of all its competitors. But over the life cycle of that fighter, the enemy would catch up, and deploy their own more competitive fighters. tThat Germany enjoyed qualitative edge in fighters during the first part of WWII was not because German aircraft inductry was superior to those of France, England or USSR. It had to do with the fact that the war fortuitously started at a time when aircraft production life cycle of the different countries so happen to be at such respective places that gave Germany a 2-3 year of window of superiority in this game at the right moment.
France and the USSR decided to fix the type of fighter upon which to hang their arms build up earlier than Germany, hence they hung their fates on an earlier generation of fighters, including the afore mentioned, and at its inception world leading and world beating polikarpov I-16.
Germany hung her fate on a later generation of fighters, such as Bf-109, that put Germany in good stead during the first half of the war. But the US and Britain was able to do so even later than Germany, with Spitfire and Mustang. Hence by second half of the war it was relatively easier for Britain and US to maintain superiority of the balk of their fighter fleets, because the basic designs of the bulk of their fighter fleets were of a more recent vintage, while Germany must struggle to field relatively small number of newer fighters while saddled with large numbers of increasingly uncompetitive derivatives of Bf-109 fighters.
It is often overlooked that a big part of the reasons for Germany spectacular success during first years of World War II had nothing to do with any long lasting superiority of German military training, doctrine, leadership, or equipment. It had to do with the war fortuitously came to Germany, against Hitler's designs, at a time when Germany was at the start of a 2-3 year window, not clearly appreciated a priori even in Germany, when Germany enjoyed advatnage in key equipment and doctrines. To a substantial degree, Germany sleepwalked into its early successes in WWII.
This kind of fortuitous leap frogging often has a lot more impact on the outcome of war between peer competitors than careful assidious long term military preparation.
I think, your statement is too romantic of hindsight. No one knew when war would start, there isn't a means to bank on a technology. Had events unfolded differently, lets say war began when the Z-plan was complete, or if France + UK pre struck Germany in... 1936; the war could be very different.
The german air force never had issues with new fighter aircraft supply, but for replacement pilots. The many obsolete renditions of the BF109 had mostly been expended during the part of the war where they were not obsolete. Germany made ~7500 FW190 + ~13,000 ME109 in 1944; both of which are able to match the latest P51, Spitfire, and any other allied fighters pitted against them.
The fact that these antagonist fighters first flew at around the same time: FW190: June 1939, BF109: May 1935 P51: Sept 1940, Spitfire March 1936, Hurricane November 1935, Dewoitine D.520 October 1938, A6M March 1939, Ki43 Jan 1939, wildcat Feb 1940; P47 May 1941, P40 Oct 1938, Typhoon Feb 1940.
What I am trying to illustrate is, there isn't a distinct age gap between the fighters; and all of these fighters served well into the war with each other competitively through their successive marks (maybe less so the A6M, but the A7M was supposed to step up to the job, but what can you say when an earthquake destroys the factory?); may it be a name change like wildcat to hellcat or ki43 to ki84, Typhoon -> tempest; they are still the same basic air frame.
Assuming the German southern offensive of 1942 (Fall Blau) as it happened: If the Soviets had not concentrated on Stalingrad the way they did, but instead they had attacked the Army Group B from Astrakhan area, they could have cut out even bigger German forces (I only read this) ... what do you think?