There seems to be two questions here; importance of artillery and the effectiveness of tanks.
Artillery was/is important as it's the best way (airpower aside) to soften up static defences. Although its damage dealing effectiveness is limited against entrenched troops, the effect on soldier morale cannot be underestimated. Against exposed infantry artillery is quite effective but has little impact on tanks.
Tanks in WW2 were used by Germany to break through at weak points in the enemy line and then to disrupt communications and supply lines to the rear. The major weakness of tanks (airpower aside) is that they cannot hold objectives. This is why the German General Staff were so concerned when the likes of Guderian and Hoth surged far ahead of the supporting infantry columns. At one point Guderian's panzer divisions were 2 weeks' hard marching time ahead of their supporting infantry.
Each of the 4 Panzer Armies in the Wehrmacht had infantry divisions to hold objectives secured by the tanks. In theory, these infantry divisions were to be motorised but very few divisions in the German Army ever achieved this. Panzer divisions had their own organic artillery component but this was modest compared to that of an infantry division. Another weakness of tanks is their vulnerability to mines. German tanks (aside from the ill-designed Elefant) had machine guns to stop Soviet soldiers getting close enough to plant explosives on their hulls etc but sometimes these were not enough. In certain terrain tanks are very vulnerable (urban, forested) and need infantry to protect them from minefields and other infantry.
I mentioned airpower twice because IMO it's largely replaced artillery and tanks as the defining weapon type in war.