Although the assault is known to popular history as Pickett's Charge, overall command was given to James Longstreet, and Pickett was one of his divisional commanders. Lee did tell Longstreet that Pickett's fresh division should lead the assault, so the name is appropriate, although some recent historians have used the name Pickett–Pettigrew–Trimble Assault (or, less frequently, Longstreet's Assault) to more fairly distribute the credit (or blame).
I'd agree that Longstreet's Assault is a more accurate name for the attack than Pickett's Charge but Longstreet bears no more responsibility for the attack than Pickett. Longstreet didn't attend the staff meeting the night before and Lee rode out the morning of Jul 3 to find him planning an new assault on Big Round Top (which Longstreet did not know were now heavily reinforced). This messed up Lee's plan so Lee changed it up and ordered a mass attack on the center. Longstreet correctly warned Lee that this was a big mistake but Lee insisted.
Lee would agree with historians that he ordered the attack, not Longstreet.
As soldiers straggled back to the Confederate lines along Seminary Ridge, Lee feared a Union counteroffensive and tried to rally his center, telling returning soldiers and Wilcox that the failure was "all my fault". Pickett was inconsolable for the rest of the day and never forgave Lee for ordering the charge. When Lee told Pickett to rally his division for the defense, Pickett allegedly replied, "General, I have no division."
But Lee enjoyed a cultlike popularity and so blame shifted in the popular imagination Longstreet was on the verge of making a different fatal mistake for different reasons so Lee's change up was not less likely to doom the Confederacy that day than Longstreet's plan but officially Longstreet objected to Pickett's Charge and carried out that attack under protest.
