That "quickly" is on the order of years (as opposed to decades, centuries, etc). If the Starlink constellation goes boom, you can't start launching new ones for several years -- and then the build-up would take years, from there.

Nah. In any major future conflict, the combatants will go ahead and launch replacement satellites immediately regardless of the risks or long-term consequences (or they'll do it at least as long as their manufacturing and launch facilities survive). A constellation of hundreds of satellites can't go "boom" all at once. Even with a bunch of orbital debris floating around the hazards will be sparse and some satellites will live long enough to be operationally useful.