I think if one were to ‘fix’ Signs, one shouldn’t change anything about the film, but rather, just rethink its interpretation – view it as a somewhat dark satire about humanity’s belief in its own specialness. Think about it: whenever aliens attack, they are portrayed as technologically superior in every conceivable way, yet ultimately, the ‘human factor’ drives them away: their computers turn out to have their anti-virus subscription elapsed, or they failed themselves to get inoculated, or some other contrivance allows the otherwise utterly outmatched humans to emerge victorious. This doesn’t limit to alien invasions – other stories where humans are faced with existential threats are essentially cast from the same mold, think Armageddon or similar.
These are essentially feel good stories: no matter what horrors the universe throws at us (which of course just stand for the perennial fear of the unknown), we’ll pull through, because humans are special. Even if the odds are slim (in a way, especially if they are), human specialness means we’ll pull through, we’ll band together to find our true strength, etc. This is a belief about us we need to get reinforced once in a while in order to go on, so to speak, in order to not get overwhelmed by the far more ordinary troubles of everyday life: if we can get our shit together, we can make it even through alien invasions, so what’s a puny financial crisis to us?
Often, such stories feature a combination of unwavering faith (in oneself, in the possibility of victory, in humanity, in god) in the face of near-certain defeat, combined with some apparently random, chance external element – ‘luck favours the bold’, ‘god helps those that help themselves’, etc. The danger put upon humanity is in fact only a test of this faith; if it is found steady, help will come, in some way.
The purpose this serves is clear: half of defeat is admitting being defeated, so holding on against all odds may be a desirable quality, and such stories reinforce this.
The thing is, however, that viewed from a more objective vantage point, all of these stories are fairly ridiculous. Humanity would have been wiped out in Independence Day, the aliens in War of the Worlds would have worn gas masks, Bruce Willis and his ragtag band of loveable misfits would have burned in Earth’s atmosphere as the meteor enters it, etc. In reality, humans aren’t special; we’re a feeble mass of organic matter clinging to the outer shell of a small rock hurling through empty, hostile space. Lovecraft knew that, which is why his horror is so effective.
Signs exposes this. Its message of ‘faith in the face of overwhelming opposition’ is so ham-handed, and its method of salvation so ridiculous, that we feel cheated out of what we expected, which is the reinforcement of our belief in our own specialness. Rather than seeing a hero, a champion of humanity, rise up against all odds to lead humanity to victory, we see a deluded fool, and the salvation of mankind occurring through blind chance (and the invaders’ idiocy). Which is, of course, exactly what we saw in all those other movies – but there, due to them following accepted conceits of plausibility, we were able to tell ourselves a different story: that in the end, humanity will always triumph, and that moreover, that triumph will be well-deserved.
Signs tells a different story: what we think is our belief in our own qualities, in our own capacities and virtues, is really just a belief in everybody else’s ineptitude, idiocy, and impotence. We’re giants – but only if we’re in the company of midgets.