Honestly it is really messed up that fireworks exist, but not canons.
Their boats have Trebuchets attached.
They have tanks and eventually full on zeppelins.
They seemingly have engines, and have had them for quite a while.
How does the war last 100 years???
They have bombs, you don't need Sozin's commit at that point.
Instead the plan was to fly the zepplins over places while firebenders just flamethrower like crazy.
What was really the plan with the drill?
Drill straight to the center of the city?
Was the drill chalk full of ground troops and tanks?
The wall can be fixed.
It is a nation of earth benders.
I assume that is how the wall got there.
At a point its like>Why didn't a bunch of earthbenders just drop the front of that shit in a hole?
At another point it is like why should anyone care about a classist city of MK Ultra loving isolationists?