The first defense line was bombarded for a consecutive six hours. In that period of time, the first defense line retaliated with 13 shots of Genesis, three shots of Requiem, and even one shot of Energy Storm.
It was then that the benefit of owning a base was truly exemplified.
In truth, the reason spaceships like battleships were weaker was due to the overall environment of space. The vacuum, the super low temperature, and air pressure meant that a small bit of damage at a strategic location could cause the spaceship to explode in space. In contrast, be it superelectromagnetic weapons or plasma weapons, the damage they could deal against buildings and objects was limited. At least the damage wouldn't be as powerful as a nuclear bomb.