You're right. The thing is I think the adoption of soapy serialization was a significant enough advancement in primetime TV (that took a long time to happen) that it's important to clarify that it took awhile and wasn't immediately established.

Hugely influential, but it took awhile and still operated in different spheres. We wouldn't have modern television without the contributions of soaps, and without having done away with a bit of the misogyny that viewed them as "women's television" and thus inherently inferior.

You can take it back to pulp fiction and earlier forms of serialized prose as well. Romance works really well in serialization, which is why once (primetime) TV finally embraced using it dramatically it became essential to the medium.

I certainly think there are radio examples, but it's interesting to see what made the jump and what didn't.

I gotta question the suggestion that the will-they/won't-they dynamic has been around since the "earliest days" of television. Maybe you're talking about soap operas, but I think daytime soap romantic tropes exist on a very different plane from primetime.