Hardee was an able and capable Corps commander. He also had the respect of most of his subordinate officers.
In December, 1863, he temporarily commanded the Army of Tennessee, but declined (at the time) the offer of permanent command. His constant disputes (1862 and onwards) with Bragg, the disagreements he witnessed between senior commanders, as well as political influences observed, probably all contributed to disincentivize him and make him unwilling to accept the extra responsibilities (and pressures) of Army leadership. Leadership responsibilities, though, certainly did not deter him from maintaining continuing active Corps commands throughout the war.
By mid-1864, Hardee was again considered by Richmond for Army command. He was the senior Corps commander, with plenty of high command experience. However Bragg's personal animosity towards Bragg, as well as Hood undermining him behind the scenes, worked against Davis making any decision to appoint Hardee to the role of Army head. It is not known for certain, however, whether Hardee would have accepted any such offer made to him in these particular circumstances at this later time. Instead, Bragg and Davis chose someone they considered would be a more aggressive Army commander, by appointing the relatively inexperienced (in senior command) junior Corps commander, Hood.
Hardee was angered by Hood's appointment, and after Jonesboro (Aug. 31/Sep. 1, 1864), he became appalled by Hood's reckless assaults and high casualty rates. He requested, and was granted, a transfer to lead inadequate forces in Georgia, then went north to command a Corps in the Carolinas campaign.
It does not necessarily follow that because Hardee declined (not rejected) permanent command of the Army that his abilities as a Corps commander were diminished, or indeed that he would not have accepted Army command later, if the role was offered again in different circumstances. In my view, he was one of the Confederacy's best continuing Corps commanders – astute, solid and reliable. Army high leadership perhaps did not suit him.