Expanding on this: in the first half of 1944 the Allied air forces were distracted by the need to lay the ground for the Normandy landing. Once it was done they renewed their strategic air offensive. Besides scorchig city after city they suffocated German infrastructure to great effect, and the Ruhr in particular was cut off from the rest of the country with a collapse in the coal supply.
Germany's situation wouldn't be all that better with a conquered East. The reason it'd lose the war of attrition in the West was the gargantuan Allied and particularly American armaments output which dwarfed anything it could ever hope to offer. The East offered more raw material inputs but not more industry. Hitler's long-term strategy was to use its living space to catch up to American economies of scale and output, but that was something for decades. In the meantime he's left with the same industrial inferiority, with the difference that his prospects of running out of raw materials are delayed and he can modestly boost his industry with more conscripted Eastern workers.
Even the raw materials situation wouldn't be vastly improved. When Imperial Germany took over the Ukraine in the last acts of the Great War it was disappointed. And now even less grain was available due to urbanization. Caucasian oil wouldn't come in easily, it'd take time to restart production after Soviet scorched earth -the Maykop fields provided nothing because of this. And the Caucausus is within range of Allied strategic bombing from the Middle East. A campaign could be launched there but it'd have very unfavourable logistics.
A substantial portion of the Heer would be unavailable, garrisoning the East. More production would be allocated to the Luftwaffe and it'd concentrate more fighters in the West but it still stood to be outproduced and defeated, with strategic bombing then taking its toll on the whole war economy. And then from 1945 onwards America would be willing to drop nukes on Germany in accordance with its "Europe first" policy.