Destructible ships generally are very fragile once the shields are down. There is a reason why most space games have a total HP/Hull.
That's because real life objects *ARE* very fragile if not protected by magic. In games, it's extremely common for an object, such as a vehicle to continue fighting until the last hitpoint. In real life, if you look at various destroyed tanks, ships, or planes, most are physically intact at the time they cease to be functional, except that key components have sustained critical damage that renders the entire thing inoperable. Inoperable ships and planes then succumb to their hostile environment. A spaceship, on the other hand, would be destroyed more in the manner of a tank than a seagoing ship or plane. Unlike a plane in the air or a ship at sea, the environment a spaceship exists in is generally not hostile to its physical existence, just as a tank on land isn't in a particularly hostile environment. A battleship of space doesn't sink, and only occasionally crashes.