The ratios mentioned by Ulenspiegel were indeed to a very large degree due to overall German inferiority in ressources and the diversion of arguably most of the technology- and capitalintensive to the 'Western' and Homefront. Very simplified the SU payed the price to defeat Nazi Germany mostly in blood and the Western allies mostly in industrial output and technology.
As Red Rat pointed out there is little to suggest that a D-Day, certainly not on it's 1944 scale would have been possible in 1943.
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