>>158843661) Materials will advance as weapons do
2) the range will severely inhibit destructiveness. Lasers spread over long distances, even in space, and explosions, even nuclear ones, drop off in power with distance. Armor prevents a near miss from being fatal
3) These are warships, they ought to be able to take a licking and keep on ticking. If this requires several meters of plate, foam, and superfluous bulkheads, so be it. It might not stop everything, but it might stop enough.