There is only one thing I agree with in the article, and that would be the intimidating presence of fighting games to newcomers, which is a combination of learning curve and community.
Fighting games are quite simply not the place for telling complex narratives. In fact, in this era where people keep trying to make movies that allow for occasional button presses as opposed to games with some cinematic moments, fighting games continue to serve as a reminder for how to keep things simple. So, it doesn't really bother me that there's some loosely related, highly generic premise for getting a group of people to want to beat the crap out of each other. The real allure of fighting games is in their characters, not their stories. People rally around an avatar who appeals to them, and then they want to win with that avatar. If you remember old-school beat-em-ups like the Simpsons arcade game (or even newer beat-em-ups like the X-Men Legends series), that very principle holds true--pick your favorite character, and proceed to kick as much ass as you can. People don't rally behind characters' stories in fighters because the stories are awesome; they rally behind characters' stories because they identify with the characters.
Spectators gravitate towards fighting games that have a character whose fighting style and aesthetic appeal to them. From there on, it keeps it simple. One person fights another person, the last one standing wins. At its core, reflexes, pattern recognition, adaptability, input memorization and basic psychological manipulation are what make fighting games so enjoyable. While other genres also make use of these elements, nothing feels so personal and 1-on-1 as a fighter. Nothing. Ever.
You say fighting games are stagnating? I say you're missing the point of them and aiming to make them into something that they're not.
If there were anything that needs to change, it's not so much the learning curve of a fighting game as it is there needs to be a much smaller tier gap. Tiers are inevitable, but as people get more skilled with a game, they should feel like the difference between their characters and others, if any, is small if not non-existent, so they feel like they can win with who they want to as opposed to who dominates the meta-game. Human error should be the bigger determinant of victory/defeat than character meta-game. That's what I think drives people away from fighters; the character they want to champion sucks horribly and the only way to win is to pick a character they just don't gel with or outright hate. Nothing is more uninteresting than a fighting game that has no characters you want to play. Character appeal/style is the most important part of a fighting game, followed immediately by balance and mechanics. Give me a character I care about playing with, and I will get good with that character no matter how difficult it is or how long it takes.
Also, as others have said, the rise of online multiplayer in fighters is probably the biggest factor in the decline of fighters. Fighters are personal games, pitting you against an opponent in real-time. While online multiplayer always gives you human opponents to face off against, add input lag and put the other person on the other side of the planet with no face to react off of and no immediacy of trash talk and the once personal fighter becomes incredibly impersonal. Yeah, I can still get together with my friends from time to time to have a few laughs, but that's becoming increasingly rare.