Burial at Sea is another awful piece of BioShock Infinite content that shoehorns in Rapture for fanservice, while not expanding upon the first BioShock game's lore or intrigue in literally any conceivable way. BioShock 2 did substantially more for the series than the useless Infinite ever did.
"Rapture wasn't special." Every reality is about a radical right winger who created an idyllic city that ultimately devolved into a dystopia, and you are transported there via lighthouse. Furthermore, a city in collapse and its residents afflicted by drug addiction apparently aren't interesting enough subject matter to stand on their own, so we must involve convoluted time jump shenanigans and give the player a Disney princess to look after. Oh, and who could forget the meaningless "both sides are the same" limpdick political / social commentary, where the leader of the rebellion is a child-killing maniac and just as bad as the religious zealot who founded the city in the first place? Of course, that gets conveniently dropped in favor of telling the story of how two blandos (Booker and Elizabeth) leapt through time.
I'm sorry about the soapbox, but Infinite actively offends me. To this day, it's still probably my most anticipated, yet ultimately least favorite sequel ever made. Burial at Sea is just more salt in the wound. I sincerely hope that the next BioShock game just does its own thing, rather than try to follow the shitcrock "lore" established by the despicable Infinite.