One can criticize Lee because he gave very vague orders to Ewell basically leaving it to his discretion to attack Culp’s Hill. He declined due to some intelligence reports and the what he considered the fatigue of his men.
If Culps Hill falls, the climactic battle gets refought further South, IMHO. Probably in Maryland. We might be talking about the Battle of Frederick, for instance.
Strategically the game was up when the Union Cavalry managed to pierce the screening forces & tell Joe Hooker that Lee was on the move northward. Hooker put the AoP on the road before he was replaced by Meade.
Had the AoP moved in its usual ponderous way, Lee would have been terrorizing the Pennsylvania countryside for a few weeks. I’m certain that Harrisburg & York would have been taken & the rail lines to the Ohio Valley would have been well & truly destroyed.