I would also be interested to hear how Stalingrad was 'not strategically important'. This should be good.
The only important thing about Stalingrad was that capturing it would allow Hitler to better reach the oil fields of the Caucasus. It would not have mattered in the long-run whether or not Nazi Germany captured Stalingrad.
1) They still had to fight the several million Russians that would just pull back and fight in another city along the way. At that time, Stalingrad wasn't the center of Russian Political power like Moscow or the nationalistic prestige of Saint Petersburg. If captured, it would just be another large industrial city that was captured during the Nazi advance. It's loss would not have been anything big. At worst, Hitler captured the city of Stalin-like propaganda.
2) Even if the Nazis captured Stalingrad and pushed straight into the precious oil fields Hitler wanted so badly(probably at a incredibly high loss), it wouldn't have matter because
A) No amount of oil is going to fix the rusting wreck that is the Nazi-wartime economy.
B) No amount of oil is going to make their military situation of over-extension any better
C) No amount of oil is going to appease the Russian Winter.
D) No amount of oil is going to let them win in Moscow and St Petersburg. Staying in Stalingrad and the Caucasus means letting Nazi soldiers be trapped into a little corridor of South Western Russia when the Soviets start to push out of Moscow and cut off their movements and supplies at Ukraine.
Stalingrad wasn't a great strategic location that must be defended or suffer the terrible consequences like losing Egypt, the English Channel or Myanmar would have been.