Hood should have left the army while his reputation as a great divisional commander was intact or not taken command .
Unfortunately, the Peter Principle usually involves the person in question reaching their level of incompetence. Because of circumstances, Hood was made an army commander. He tried to delay taking command until after the Battle of Atlanta (as an engagement at Peachtree Creek was imminent) was fought, but Davis and Cooper insisted that the change of command take place immediately.
One question: How do you hold a city or a fort that you have the intellegence to realize that you will not be able to defend.against the force that are advancing against your limited resorces and they can matain a siege for a length of time? Johnston could not defend Atlanta with his army.Could he have wanted to find area outside more open to battle Sherman.Could he have thought of the general population of Atlanta in his decestion ? If one knows that he is in a indefensible position would it not be wise to seek a position where you might be more adverse for you.Atlanta would have fallen even with LEE.. PETERSBURG
Except did Johnston argue that Atlanta was indefensible? He had no plan at all. At least no plan that he would communicate to his superiors or his subordinates and that has survived.
In an ideal war, the commander is supplied with enough resources and manpower to accomplish his objective and maintain the initiative. However, war are from ideal. Johnston had an objective (hold Atlanta until November) which he had to make do with the army he had (and helped to shape). It is noteworthy that Lee, in a much smaller theater of operations, held Grant in check for much longer while facing greater odds (despite Johnston's claims to the contrary). It is noteworthy that Lee managed to hold Petersburg for so long in part because he aggressively checked attempts to cut the various railroads into Petersburg (Globe Tavern and Weldon Railroad come to mind) and even launched numerous small tactical offensives. Hood tried a similar approach with Atlanta and failed, bloodily in some cases.
There are plenty of explanations for this. The Army of Tennessee was not the Army of Northern Virginia. Lee's men were confident in his proven generalship and even revered him. The rank and file of the Army of Tennessee had endured Bragg, was concerned at Johnston's constant retreating, and even more concerned at Hood's replacement of Johnston. Even late in the war, Lee could count on Gordon, Mahone, Heth, Field, and a returning Longstreet to manage field tactics. Who did the Army of Tennessee have? Hardee, who was so frustrated at Hood's promotion over his head that his performance suffered and he may have disobeyed orders at Peach Tree Creek and Bald Hill. Cleburne and Cheatham excelled on the defensive, and there were a few talented and capable officers like Walthall, but there wasn't really more than a handful of officers who could coordinate offensive tactics in the army. By contrast, the list of officers
incapable of tactical articulation at higher levels is much longer at starts with corps commander S.D. Lee. By late 1864 the worst thing you could say about a division commander in Lee's army was that he was only competent and not brilliant (with the exception of Pickett, perhaps). In Hood's army, Stevenson and Bate were not fit to command divisions while Walker and Loring were troublesome off the battlefield. That's more than a third of the infantry commanders.
It is also worth noting that the Army of the Tennessee and Army of the Cumberland were not the Armies of the Potomac and the James. Except for Chickasaw Bayou and Chickamauga, these men had never known defeat and, to paraphrase Pope, were pretty used to seeing the back of the Army of Tennessee as it retreated. While Sherman may not have been good at tactical articulation (very few army and army group commanders were or are), he was an excellent operations chief and he had Thomas and company for tactics. I have never intimated that defending Atlanta was easy. With this opposition it was going to be hard. But wars are never easy.
If Atlanta were indefensible as you claim, then Johnston's best chance at defending Atlanta was to fight the battles as far north as possible. While an offensive into Tennessee may not have been advisable or logistically probable, Johnston may have held Sherman in check if he changed base into Alabama and moved to threaten Chattanooga and Sherman's communications and supplies while keeping a holding force to Sherman's front. But Johnston did not do that. He retreated from Rocky Face Ridge to Resaca, to Adairsville, to Allatoona Pass to Dallas-New Hope to Marietta and then to the Chattahoochee. And when he retreated across the Chattahoochee, there was no more ground left to give aside from Atlanta itself. And if he abandoned Atlanta, he might have avoided the 12,000 plus casualties Hood suffered, but he would have likely suffered desertions (especially in the Georgia troops) to add to the 16,000 casualties and desertions he lost on the retreat to Atlanta.