There’s a whole genre of sci-fi that has a major premise as “humanity is the most powerful/dominating/victorious species in the cosmos…and that’s not a compliment”. I always understood that to be a facet of HFY, but per this sub’s description HFY should be “uplifting”.
Like, a story where aliens try to invade Earth and we kick their asses is definitely HFY. But what if we then enslave the survivors of the alien horde? What if we reverse engineer their tech, go to their homeworld, and nuke their planet? What if we tailor a virus to their genome and purge the galaxy of their entire species, and their little alien babies die screaming in their little alien cribs?
Is that HFY?
HFY in the modern sense was originally the result of angry neckbeards being triggered by James Cameron’s Avatar and venting by writing a bunch of stories that basically boiled down to “chad humans showing the virgin xenos what for (usually via mass murder)”. After a while people calmed down enough (or enough non-angry neckbeards got drawn in) to start expanding beyond that original concept, which is when we started getting more “humans are the tide that lifts all boats” and “humans are weird and that’s OK” style stories. So yeah, I agree that even if the genre is more that that nowadays, it’s still a fundamental part of it.