So if Octavian's first marriage wasn't important enough to mention, why bother with his second? I think they just wanted to have Livia in there, and bank on some of the audience's familiarity with her reputation as a manipulator and poisoner to make them keep watching in hopes that she'd kill somebody.I think that there's a sizeable difference between ignorance and stupidity in this case. Scribonia was not important to the story nor would she be, given the cut-off point, so the conservation of detail probably made the final chop. What you're saying would have been better historically, certainly, but I was far more bothered by Vorenus' children never ageing throughout the life of the show. That final shot of his children being rescued from captivity was a total immersion-breaker for me.
I'm not saying this isn't the only thing that bothers me about the series, and you're right to point out that Vorenus' children were poorly-written as well. And how about the idea that Pullo was Caesarion's real father? That just screamed "SOAP OPERA SHENANIGANS!" to me.