I agree .On the presidency and generally on the era I suggest McDougall’s “Throes of Democracy”. He is a gifted though arrogant writer but his work has led me into my Third Civil War Revival (this time securely if critically pro-USA).
Grant had the greatest needed attribute of a general. Not giving up. If Lee was serious he would had thrown down the towel once bottled in Petersburg. Continuing the fight at that point was pointless slaughter. Grant could had fought better at that point, but Lee bears the responsibility.
The sad reality is that as you point, once outflanking via the sea became impossible the campaign became a bloody battle of attrition. This is similar to the Paraguayan War, were until Caxias used naval-army cooperation to outflank the Paraguayan strong-points, all the Allies could do was bloody frontal assaults.
And ultimately you can only do so much against an enemy that refuses to understand the war is over. Whether that is Grant , or Caxias, not everybody is as lucky as Guillaume Henri Defour, who was indeed brilliant, but also helped by an enemy side that ultimately had no stomach for war to the finish (Sonderbund War).