I've been playing D&D for 30 years now, and even when a round was a minute long, it was clearly only six seconds long. Nobody I ever played with imagined their character's actions as an abstract series of attacks, parries, and dodges. One die roll has always been one action.
When people look back on their favorite D&D battles, they don't remember the time they abstractly traded blows with their enemies. They remember the times they took specific actions that corresponded to the dice rolled (e.g. "Remember that time I swung across the room on a chandelier, dropped down behind the villain, and backstabbed him?").
And it's nice to say "make the round a variable length of time" but what do you do when one player wants to do something *fast* and one player wants to do something that makes more time? You've gotta have some basic standard, and then you can arm waive around the edges as necessary.