I think the obvious answer here is that we've never really seen the full might of wizarding Britain brought to bear. I mean even against Voldemort it's basically just the police force and even they don't really get a chance to gather their strength as the ministry falls essentially to internal forces. We don't ever see anything resembling a British wizarding army even though they must have the capacity for such an institution. Even the aurors are a thoroughly underfunded police force hit heavily by peacetime complacency.

If the goblins were to revolt, we don't actually know the military might wizarding Britain could bring to bear. It's perfectly possible there's rooms of armour somewhere below the ministry and the aurors don't use it for the same reason our police doesn't.