When I say drone Im not specifically talking about pizza boxed sized ones with rpgs jurry rigged to them. Im talking about Predator/Reaper sized drones.
In a non retarded world a small craft capable of carrying 1000-2000 pound payload would be trivial to mass produced.
This isn't just an engine with a computer on it that you program to go to a spot and drop bombs, these are piloted. You need a pilot, Tactical Command and Control of the airspace, so a RADAR installation, network capability. On top of a ground crew, of 7-10 to receive each drone as they land. On top of the supply chain for parts, and fuel. A Reaper sucks up 4000 pounds of fuel. Not to mention the need for precision guided ordinance that they require. Something equivalent using dumb bombs, would just be a big fat target. No one drops a dumb bomb at 25000 feet with the expectation it's going to hit something pertinent unless they drop an apocalyptic amount. So now you just have created a worse bomber.
I also don't think you realize just how big a MQ-9A Reaper is. Its wingspan is 65 feet, and it's 36 feet long. Now it can carry 3800 pounds of ordinance. However that is across 7 hardpoints. Due to only having 7 rounds you can't use it to breech a defensive line. It will drop rounds, and then head back for rearm and repair. So you won't be seeing that drone for several hours. The hours to transit back behind lines need to be taken into account as well. Even if you had 100 drones, that would give you 700 rounds to fire. A modern artillery piece can fire 2 rounds a minute on sustained fire. 10 guns can fire that in 70 minutes, and they keep firing.
I won't get into the command and control nightmare and airspace management to keep 100s if not 1000s of drones from bashing into each other. All aircraft are magentically attracted to each other, and they want nothing more than to smack into one another, no matter how big the sky is.
Have you ever seen an tube artillery unit in action? They are not agile. Counter battery fire is a massive threat to tube arty, especially tubes that arent self propelled. And they have a long logistics trail behind to support those 7-10 dudes per gun and the two trucks minimum to haul that gun and ammo.
In GWOT where you could park and forget a gun, that wasnt a problem. Its gonna be a problem against a near peer in a total war scenario.
I have seen artillery batteries in action. I've called for fire too. If you are receiving artillery fire, as an artillery unit. Multiple fuck ups happened. Somehow unbeknownst to you, the enemy has found where your artillery is, which is of course possible with modern ISR. Then, they advanced to a position that is unknown to you, which is a failure of your own ISR and recce, within range to engage your artillery.
However, there is this magical thing that an Howitzer does, which is just leave. You start getting shelled, you pack up and run away. It is really easy to move an artillery battery it's trucks, brute strength and ignorance, the army's chief strengths. Its even quicker when you are propelled by the terror that comes from being shelled. At the same time, because artillery is sighted to provide overlapping fields of fire, and if they can hit you, you can hit them. The battery next to you, will probably now have sighted the unholy amount of smoke that artillery kicks up, and begin to return fire.
Ironically during the GWOT, artillery was less effective than drones. You weren't breaking a defensive line, you were dropping a bomb on some dudes in a truck. The Reaper was great for killing goat herders. It was great for when you are like "fuck this house in particular.