While that's always been a problem (and we do have plenty of examples of female iterations eventually SURPASSING their male counterparts, like Captain Marvel), there was still quite a bit of them out there at this point.
Electra Woman and Dyna Gal for life!
Fantastic Four had Invisible Woman as a founding member and I know it had a TV presence way back when.
But you are right. There were (and remain) few original, non-derivative superheroines. But I think the concept as grown on me over time as the women were written more and more independently of their male counterparts.
The 70s comic scene in particular was giving us a ton of unique female characters - Starfire, Raven, Black Canary, Big Barda, Storm, Rogue, Black Cat, Scarlet Witch, etc.
Shame they didn't get a big media push until much later.