Wrecked railroads but intact vehicles. Bombing the railyards prior to DDay provided that tactical advantage of forcing road marches. By the mid 1944 many things had changed in the war. Leaving production unhindered wouldn't have helped the Eastern front which likely would have affected mid-1944 in a negative way for the Allies.
The Germans were good at repairing factories and later, at dispersing and hiding them. Production never suffered that greatly from bombing. Their production was actually trending UP througout of the war.
There is some argument that bombing’s greatest contribution was the quantity of resources diverted to the Defense of the Reich.
Their real bottleneck was oil. They lost their eastern oilfields and had to depend on synthetic fuel - and those refineries were hard to hide.
And then there was the issue of trying to move that fuel.
So, even if the Germans built stuff, they had a hard time flying or driving it. A significant part of the Battle of the Bulge required the Germans to capture Allied fuel dumps so that they could keep going.