The Senshi are not trained professionals like Nanoha, Fate, and the Wolkenritter. In some ways that makes what they were able to accomplish more impressive. In modern terms, their actions are like a self-recruited, self-trained part time militia
formed of people who had no combat experience beyond schoolyard scuffles before being recruited, no logistics, a shoestring budget, and the closest thing they have to medical support is someone who plans to apply to medical school at a point several years in the future. Said militia then ends up being the only line of defense
against a considerably larger enemy force, with no way to detect an impending attack until it happens and no way to launch an counteroffensive, even if they knew where they were supposed to attack. And then they manage to successfully hold the line until real professionals learn of their situation – a year and a half later
. There are undoubtedly a lot of things they could have done better. That doesn't in any way change the fact that they managed to accomplish that much is an astonishing achievement.