It's a brutally swift sequence, the Defiant goes from kicking ass to being a wreck in about 90 seconds. It's genuinely quite sad too, especially Sisko looking forlornly back on his bridge one last time. It was a gutsy move to kill off the show's hero ship, even though it does get replaced by a near-identical ship with an ugly carpet.
I think the destruction and replacement of the Defiant
is an interesting moment.
In Trek there's a history of the ship almost being a character, and I think that's certainly still true on DS9 to an extent, thought the show is built more around the station and the wormhole than the ship.
does really fit the show's identity, in a way, though: the tough little ship, stripped down to the essentials, not really built for exploration, but for defense, and for war.
It's also very much established as a force to be reckoned with at this point, so its destruction does hit pretty hard.
On the other hand, I find its immediate replacement to be appropriate: there's only so much time that can be spent caring about a warship in a conflict like this.
Some have said that replacing it undercuts what previously happened, but I don't think it really does. The attachment the characters might have to the old Defiant
is based on the experiences they shared on it, not its "uniqueness" as a machine. Also, it's just a ship. Let's not get carried away.