But it was not fire that broke apart any part of the wall; it was force. An airbending or waterbender could have done the same thing. Firebending has not been shown to be any faster than any other style. Most of the firebending we've seen in fighting has been simple techniques. Simple punches and kicks. All the styles have the same progression of complexity. They all can do various simple things that can be used to devastating effect. The more complex or powerful moves require greater movement. Toph's senses provide her a slight advantage over actual sight. Anybody with her level of skill and ability can do the same thing.

Yes, lifting a boulder from the ground does require more time since it requires more focus and energy. By comparison, simply pushing a rock requires stepping out into a wide stance and punching. This is almost the same set of motions a firebender uses to throw a small fireball. Katara didn't wasn't drawn into the ground because she was to slow. She was focused on all of the stone disks angled to attack her. Also, the general didn't use any fancy motion to do it. He had is hand to his side and made a large gripping action. As he lowered her deeper, he kept closing his hand a little more until he completed a fist to bury her. A small, simple action used to devastating results. Casting lightning is still a high level technique that takes time to perform. I would still not use it for assassination due to the amount of light it puts out, and you'd want a clear path. It would be just as easy to use a fire blast. An airbender would be able to do the same thing as we saw him possibly dismember a buzzard-wasp. An earthbender could smother with a simple move. A waterbender could drown someone. Channeling lightning is a technique that can only be used on an unsuspecting opponent. That makes it almost useless. A prepared waterbender could form a puddle at the firebenders feet and use that water to form a water shield. The lightning will hit the water shield and course right back into the firebender.

The firebenders are no smarter than any other nation. They worked to create an advantage for themselves while the other nations maintained peaceful balance, and the Fire Nation's armies are larger in number. It was the ambitions of the Firelord, not the style itself, that brought about those new inventions. Within history, Western nations took and improved the inventions of eastern Asia. It is only within the last fifty years this has reversed to where the East Asian countries are improving upon the inventions of the Western nations. Does that mean that the Western nations were more intelligent for being the first to improve upon the inventions, or are the Eastern nations more intelligent for being able to turn the tables and do it better? The Fire Nation is winning because they have had more strategic victories. The use of the new technology is a surprise tactic and ruins standard tactics. But the Earth Kingdom has been holding them back for 100 years. The Fire Nation has not been winning simply be analyzing the styles of the other nations, but they use technological superiority and sheer number to overwhelm their opponents. It is hinted at more that the Fire Nation completely disregards the other nations based upon the lesson Iroh gave Zuko in Bitter Works and the speech that General Zhao gave to his men in The Blue Spirit.

It's fine that you like fire the most. The problem is your reasons and the assumptions made. Ultimately, your reasons are about the people, not the style itself. As you said, Zuko was able to beat firebenders with just martial arts. Though, it was the martial arts for the twin broadswords; he was able to beat a series of firebenders with just martial arts. The earthbenders on the prison rig were able to beat the firebenders once they had something to bend. No one style has ever been shown to win over any other consistently.