Are we getting worse results though? How are you determining that? Russia has always gone for the volume strategy in basically everything. It's basically the zap brannigan special of throwing meat into the grinder until it clogs using cheap, mass produced crap.
The US has gone for high tech and precision. Costs much more, much lower production, but generally better results.
Also Russia is in a "hot" war with Ukraine and of course will be well into mass producing shells to use etc. Seeing as the US is barely passing measures to send aid to Ukraine, there isn't going to be an appetite to ramp up that production.
Look to world war 2 for an example of how the US can go from no real military might to okay you touched our fucking boats, now we end you.
So why hasn't Russia taken over Ukraine?
And why are you bringing Stalingrad into this? You are literally saying it's a good thing that Russia is producing more arms etc and then saying Russia doesn't tend to operate by trying to use overwhelming numbers? Huh?