its supposed to be more industrialized due to the fact they have control over fire and therefore smelting and such metalwork is much easier, although much of its designs come from extorting EK engineers to make war weapons.
Yes because the fire nation posessed so much territory from the earth kingdom there should've been at least a couple of earth kingdom scientists that they could threaten to burn down their town (temple in the mechanists case) if they didn't offer their services to the fire nation. And the fire nation started with a small amount of technical developments (minimal) 100 years ago and because then people could study for ingenieur or something like that in the direction that has to do with technology and the more people work in that direction the more people suddenly think: H? I've got an idea that will help our nation. I think that the fire nation is the smartest nation (I THINK don't kill me if you're from an other nation)
Lawrence you're right it gives the fire nation dominance at see because our boats are stronger alright it can't handle a sharp iceberg that pierces through the bottom (SoTH1) but it gives protection against (flaming) rocks (The Awakening) The wooden ships of the watertribe are easily penetrated by the (flaming) rocks and I think earth kingdom ships as well (even though we have never have seen them[but I think they do excist because in The Avatar State general Fong said that they get slaughtered before they reached the fire nation so I think they get there by boat] I think they're also made of wood) And yes firebending can make metalmaking easier because you won't need a huge furnace but you can just throw the bits of iron in a jar and then heat the jar in your hand and make a sword of it for example. And It wil almost never fail because you control the flame you don't need to throw on more wood or charcoal.
The fire nation is the richest country out of them all. And the fact that earthbenders dont want metal because they cant bend, and waterbenders dont really want it either so that leaves the Fire Nation.
Powerofinsanity put it best. The fire nation definetly is the richest so they can afford to invest in advancing their technology. The airbenders are no more and the waterbenders use basics as technology. Seems like earthbenders are the next nation to advance with technology.
Airbenders don't excist anymore and they would never use metal the Watertribe wouldn't use it either (they don't have the resources) The earth kingdom does make metal (They put long feng in a metal prison, master yu and xin fu locked toph in a metal cage etc) I don't know anything about the wealth of the earth kingdom. They don't do much with it because they don't want to they just want to stay earth. Or they don't have the money for it. The fire nation has the money for it (though after 100 years of war maybe not anymore) but they have the most to gain if they use metal. They used it to have the upperhand, strong metal ships, slingshots, armour etc. But they also invest in normal things.
The Fire Nation would definitly be able to create some new technology for the ATLA world. The ability to bend fire would be able to melt and manipulate metal, create steam propelled engines for vehicles, they already have the balloons powered by fire. The ability is there to create new technology for the Nation and maybe the (ATLA) world.