The key failure in German accounts of the war is their lack of understanding of the Red Army and
their operational level of war and massive organizational change experienced in phases during the war. This is because the Red Army operates in a manner that is very much alien to the armies in the West. This lack of understanding extends to the impact of thinking and planning on this level. Germans tend to apply perceptions that are valid at the tactical level to the operational level, which is an error. These tendencies are prevalent throughout most of their interviews and memoirs, and so forth. A few weeks ago I read the 60 page transcript of US armored commanders interviewing Panzer General Balck at Chir and he and Mellenthin displayed these very traits.
A very common thing in German accounts is for a division commander to proclaim their 'superiority' over the Soviets while being outnumbered for a couple of days. Meanwhile, their entire army is getting defeated and will retreat thanks to the events of these days. They cannot grasp the reality of the situation, and learn the wrong lessons from their experience.
To start with, you are of course correct that contemporary German perception of the Soviet approach merits particular caution and has its intrinsic limitations - thats historiography 101. But:
When it comes ie. to the intelligence picture, German insight actually increased exponentially past the beginning of Barbarossa, (before the war it was in most respects abysmal - as evidenced by the fact that it underestimated Soviet strength by almost 50 %) and so did the quality of FHO, their assessments of Soviet strenghts, casualties, and intentions proved by and large fairly reliable whereas the Soviets often operated in the realm of fantasy. The official Soviet history of the Great Patriotic War makes for interesting reading in this regard. As for the alleged German reluctance to discuss their failures or apologetic tendencies in general, this has some truth to it when it comes to particular generals' memoirs (ie. von Manstein etc.), but in general, it is quite simply wrong. If anything, if one constrasts the German tactical treatments, lessons learned etc. with their Soviet counterparts, one is struck by the German willingness not only to discuss their own personal, operational and doctrinal failings but also by their acknowledgments of perceived Soviet superiority in several fields - even though the Germans overall, unsurprisingly, perceived themselves as superior. Soviet analogues on the other hand often, for the lack of a better word, appear borderline bizarre and read more like hagiograhic accolades interspersed with agitprop jargon then serious military literature - for instance, failures (if discussed at all) are virtually never explained in terms of German agency or performance but at most by material shortages, and more commonly by misapplication of political derivatives/"military science" or the shortcomings of certain vilified individuals...
If you read German, look up ie. Middeldorf, Eike: "Taktik im Rußlandfeldzug", and go from there.
A key weakness of the Germans is their excessive focus on combat operations, efficiency, tactics, and troop training at the self-contained division level and below. They maximized logistics support and human & material resources at this level while neglecting the higher levels. (..while not improving their military intelligence arm, military engineering, logistics, artillery, and developing strategic offensive capabilities at Corps, Army, Army Group level)
A German infantry division in the offensive consumed up to 650-550 tons plus a day (this includes 200 tons of artillery ammunition or more), while 1.5 Soviet divisional equivalents consumed only up to 270 plus tons a day in the offensive.
Soviet forces were literally the opposite in focus; You have thinly supplied divisions but very powerful strategic and operational organizations (corps level and above) that were used infrequently. The military philosophy and priorities were completely different between the two, but many German commanders saw things from their own 'frame of reference'.
German military intelligence was poor in the war in the east overall. It was good (only in terms of the border) in the summer of 1941 because they studied Red Army dispositions between 1940-1941.
Let's see: In 1941 they destroyed about 1/3rd of Soviet armies, but failed to detect the presence of half of them. In 1942 they failed to detect soviet armies in STAVKA reserve, soviet mobilization capabilities, and only destroyed or nearly annihilated maybe 7 out of 83 (?ish) armies in 1942. They also failed to understand the significance of periodic and massive changes in Soviet forces structure, including the Tank armies, Sapper Armies, and the Artillery penetration corps.
At Stalingrad and Kursk, they completely failed and simply walked into a trap to suffer massive defeats (Uranus, Orel, Kharkov).
These are just some of the reasons why old fashioned, German historiography from divisional commanders or apologists (which claims that they were winning until Stalingrad, and lost at Kursk) are wrong. It even contradicts a few, lonely voices. Chief of German Staff General Halder, before he left his post in 42', considered the war to be lost in 1941.