User blog comment:Suparockr/List of Plotholes throughout the series/@comment-5267262-20120721102720/@comment-5267262-20120729164529

@GreatEmerald kinetic barriers around spaceships is where hole 3 is manifest. Otherwise the alliance fleet would have been able to cause some catastrophic damage to the reapers (while in themselves being wiped out) in orbit above earth in the opening sequences of mass 3. The geth-quarian war in mass 3 would be over in minutes to hours rather than at least 17 days. No one would bother making dreadnoughts since they would be unable to stand up to frigate or cruiser fire; everyone would focus on making very maneuverable frigates with a few cannons firing high explosive rounds rather than large ships with kilometre long guns firing huge metal slugs designed to break through a barrier with enough spare energy to induce damage. Furthermore the whole military doctrine of every force in the galaxy would be about getting into atmosphere as soon as possible so you can resist enemy fire rather than securing orbit around a planet and then bombarding it, this would be another reason why dreadnoughts and cruisers would not be built; they are too heavy to survive in atmosphere without falling to the surface (according to the codex, broken in opening of mass 3 when a dreadnought and reaper are battling a few hundred metres above Vancouver)