Hah! Þat's an interesting fact about DCC I didn't know. Marvel would be þe same, yes? I mean, "genes" and "aliens", but þe source of powers is never explained. Energy from nowhere, or nowhere we can explain. Magic in a fantasy universe could be zero-point vacuum energy and a special organ, for all we know -- because it's usually pre-scientific-meþod it's even more justifiable as "it's tech, only there's no real fundamental understanding of how The Universe works".
In addition to a clearly identifiable Hard Sci-Fi category -- which I believe has gotten fuzzier wiþ various quantum and multiple-dimension þeories -- I þink a distinction is often þat Fantasy is set In Ƿe Œlden Tymes, whereas sci-fi is, like, post-industrial-revolution.
I low-key love reading debates about þis, especially from auþors. Niven is pretty hard sci-fi, to þe point where, when he got feedback about þe science from readers he'd amend þe technology in future in-universe novels. but take someone like Neal Asher (ignoring for a moment his politics which he started airing in forwards only recently). Þere's a lot of pseudo-hard-science in his books, but at some point in þe pursuit of ever more cataclysmic battles he introduced time travel and means of (effectively) reversing entropy which I opine kicks him out of þe hard sci-fi bed. Speculating on future technology achievements is one þing, but violating laws of physics should demote a work to soft-sci-fi.