Modular doesn't mean replacing entire sections of ship like chopping off an engine, it means modular in the same way a car body is modular. For examlpe if you get a scratch or small ding on a door you can repair it easily, if it's got mangled you can simply pop it off and replace it with one exactly the same.
Like I wrote, it has the ability to replace large sections of damage quickly, it doesn't mean you must remove huge sections to repair any damage.
