I'm not talking about reusing assets. I'll requote from previous page and maybe you can give a better explanation.
I don't see how developing this:
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is supposed to be any easier than developing this:
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You seem confused mostly because you can put a pen to paper and make a 2D image right now. Even if it is terrible, and if you have no idea how hard 2D animation that looks good actually is, you are convinced that this is quicker and easier than 3D because you feel like you could do it.
You also seem super confused about game logic, and even though a few of us here have given you really valid explanations, you are struggling to understand. Again, you should grab Unity or Unreal 4, do some tutorials, and put together a simple game. You'll learn a lot.
Details - Drawing one image of a 2D character is extremely easy compared to making a good 3D model of a character. This is why the concept art stage is still always done in 2D. However, drawing 10,000 frames of 2D animation, the traditional way, means starting from scratch every frame. Even if you use flash-techniques to bend and manipulate parts of the image, using keyframe and interpolation/blending techniques, it can still be extremely expensive and tedious and requires extreme levels of training and/or talent.
In 3D, once you have built and rigged (applied a bone structure) to your character model (which is expensive up front), animation is a matter of posing the model like a doll. This is so much quicker and easier than 2D animation, but still requires talent or training. Animations are applied to the rig (the bones), and other characters with similar bones can have animations re-targeted to them, saving a ton of time as well. Making changes to existing animations is also vastly easier, making prototyping less risky.
Everything else you seem concerned about is all just game logic. You need to think in those terms. Why can a 3D fighting game character move around the stage? Well, because he was given a move that lets him sidestep left and one that lets him sidestep right. The stage has collision on it so he doesn't fall through the floor and can't pass the walls. The wall's collision parameters are tagged differently than the floor so that characters can bounce off of them when they are in a hit-state flagged with 'wallsplat'. All of this exists in a 2D fighting game as well, except we've locked the characters to the Y and Z planes. All the same rules, all the logic, is still there.
Lets look at attack reaction states. If the gameplay is 2D and I hit you, I have Y and Z values for how far "away" and "up" I toss your body. If the gameplay is 3D and I hit you, I have X, Y, and Z values for how far "left or right", "away", and "up" I toss your body. Its just an extra value, one that you are probably dealing with as a constant 0 in a 2.5D fighter anyway. Again, the logic is the same, you just might have an extra variable. An extra variable is a feature. Depending on the complexity of this variable (for implementation and balance) the budget will go up. Features = Time = Money.
I also find it offensive that you've compared a clip of 100% finished release assets in a AAA budget game with unfinished sprite work in an indie game.
I feel like the answer as to why there hasn't been any new 3D fighting game IP's is simpler than you'd think- fighting games (both 2D and 3D) are hard and expensive to make, and are a significant risk if you're a developer. 3D fighters are a niche of a niche. Therefore, not as many new 3D fighters.
Bingo.