And they were stuck there for basically the past 2 years until the Russians collapsed, which rather nicely shows they were at their limits.
Nah, it's mainly because the Germans are logistically in '39 much weaker compared to their '41 offensive. You know the saying about amateurs and professionals...
Why yes I am familiar with that quote... which is why I keep mentioning the importance of all those trucks seized from the West in 1940.
Really when you look at it, the maximum Nazi advance in 1942 is little different from their maximum advance in 1918. It really comes down to the railroads in the end, and they were not substantially different in either year. The mechanized forces of the 1940s were faster in operational terms, made encirclement battles easier to accomplish, but when you add the weight of their logistical needs to the equation it still means that the War in the East is based on the railroads.
"Supplying War" made that point very well but you can also see it readily by comparing a map of German occupation in 1918 to that of 1942.