Meade lost three of his seven infantry corps commanders. Maj. Gen. John F. Reynolds, a fellow Pennsylvanian and career Regular with whom Meade was close,
Likewise, Maj. Gen. Winfield S. Hancock, commander of the II Corps, was badly wounded during the repulse of the Pickett-Pettigrew-Trimble attack on July 3. After Reynolds fell, Meade sent Hancock to Gettysburg to take command of the field and to determine whether it was a good place for the army to stand and fight. Hancock had been magnificent throughout the entire Battle of Gettysburg, and his loss was immeasurable.
Finally, Maj. Gen. Daniel E. Sickles, the commander of the III Corps, while an amateur soldier, was nothing if not aggressive
Thus, having lost his most aggressive commanders and saddled with very inexperienced corps commander, Meade had nobody to advocate really aggressive activity. Further, he lost the two subordinates he most trusted and depended on most heavily in Reynolds and Hancock, and instead had to rely upon four inexperienced temporary corps commanders in Newton, Hays, Birney and French.
The Army of the Potomac had used up much of its ammunition and supplies at Gettysburg. The limbers of its artillery units needed to be refilled, and so did the cartridge boxes of the infantry. Meade’s logistical chain needed time to re-supply the army. That practical necessity also hindered Meade’s decision-making freedom. The Army of Northern Virginia, by contrast, had been receiving supplies around the clock at Williamsport. A small ferry called Lemon’s Ferry carried Lee’s wagons across the Potomac River one at a time and returned with crates of supplies. The ferry ran twenty-four hours a day, and each trip brought back more ammunition and other supplies. By the time that the Army of the Potomac was in position to attack, Lee’s Army of Northern Virginia had been fully resupplied.
A severe set of thunderstorms set in the night of Lee's retreat. By morning, most of the roads were impassible and untenable for any heavy artillery et al.
Regarding how Mead is perceived today, it is important to realize that a major campaign against his reputation had begun shortly after the Battle of Gettysburg: Sickles, Butterfield, and others had personal scores to settle. Hooker still had a strong following with powerful folk supporting his return to leadership, Halleck was a friend to nobody and very adept at talking out of both sides of his mouth (some might even say duplicity), and the Joint Committee on the Conduct of War had an agenda within and agenda. Mead had very few allies
https://emergingcivilwar.com/2015/07/09/civil-war-witch-hunt-part-iii/