The prototypical soap opera was a show like General Hospital. These aired for 30 minutes every weekday. They were cheap shows to begin with, and at that tempo, they pretty much had to be done live, or in a live (3-camera) format with very simple editing. They were so cheap they didn't bother filming or videotaping the as-aired episodes. Needless to say, they're not meant to start watching at episode 1; you're expected to join the fun today and then tune in tomorrow, and they're written to encourage that and to "hook you in". They certainly didn't deal with "big For that reason they avoid "big head" stuff like revolution plots or intergalactic wars, because that's too hard to join in the middle. That's what makes House of Cards not a soap.
But the writing makes them a "soap" - it wasis hasty, and was all about interpersonal relationships, because that's universally appealing and easy to film in simple sets. There is high drama amongst the characters with arcs across many episodes. But not a lot externally - No high-concept stories, no epics, no world-changing story arcs. Johann might spend a season stealing Karen's inheritance, but they'd never spend a season helping the CIA catch Iranian spies.