I don't believe in blaming Ewell alone for July 2nd's failure. Ewell's orders were to make a "simultaneous demonstration" until the "opportunity" for a real attack presented itself. If Longstreet had been able to roll up the Union forces toward Cememtery Hill, then Ewell would have the clear opportunity to attack. Longstreet's failure to push the Union left upon it's right could explain why Ewell had a problem finding that opening.
David