I used to think this way, until I tried writing more sci-fi and I kept running into weird moral quandaries trying to keep stuff realistic on a human level. I genuinely don't think there will ever be a threat that could rally all of humanity at this point. Not only because I don't believe aliens are a thing we'll ever experience, but also because everything I've seen points to people being too chaotic. Even the perfect enemy (some bugs that just want to kill us all) would have humans helping them out, a contingent of people who think the whole thing is a deep fake, and a multitude of people preying on the flawed reality of those groups and others to horde whichever resource (money, food, manpower, etc.). That's before you even get into the various well-intentioned factions that would form around a variety of "best" approaches to the issue.

I'm not even saying this in a doomer kind of way, I'm rather optimistic and believe we tend to stumble forward. I'm just saying the rally around the flag moment for humanity feels like a total fantasy.

Except the fictional "fixing" of humanity involves an inhuman "enemy", a thing that very much happens in real life (dehumanizing others in war or oppression), which tracks because these things are satire of that real world scenario.

All of this is to say that embracing the fiction without that distinction as satire really just enforces those innate bad impulses you brought up, and we have enough of that right now, imo.

I feel ya. We need sole aliens out there for us to mostly stop hating ourselves.