Or if you regard reducing hit points as reducing a rather nebulous thing that amounts to "the things that keep X in a fight" and when they're reduced to zero that's the "And now I can't fight any more" point.
To be fair, Mike Mearls is not the most articulate person I've ever encountered, or at least his columns don't make him out to be.
Game designers' vocalization skills are besides the point, what matters are the rules they produce. The D&D Next rules are largely great, which is precisely why this one sticks out so much.
Your first point about "I can't fight anymore" is kind of absurd too, it's not like kobolds can't fight anymore vs any other opponent who missed them, it's only this one fighting style guy who tires them so quickly, that they just keel over and die, despite the fact that their weapon flew right over their head.
After a while, that gets old. If you play the game like a game of chess, sure, it doesn't matter that the narrative doesn't make sense, that you've killed hundreds of foes by exhausting them to death after a handful of seconds. But that kind of absurdity does matter to many of us, who also realize that if you're going to narrate why missing is so tiring vs the Gweefer, why is nothing else the kobold does all day tiring in any way, whatsoever, including fighting any other combatant versed in some other fighting style.
Just wait until a DM-run Ogre Warrior uses his pike to kill your wizard hiding behind your fighter with Protector, with 100% certainty, and no benefit or "protection" offered by that fighter.
When the DM kills your PC by asking you how many HP do you have? 5? "Ok, sorry the ogre kills you now", without rolling even a D20.
The dice need to have their say in D&D. GWF bypasses the agency of both the D20 and the W dice. It's terrible.