There are two main storylines.
One: Where Jack comes out of third-stage syphilis delirium and leads a diverse rascal band of former galley slaves on a wild quest to steal a boat-load of silver, then return with it back to Europe via the Pacific.
And Two: Where Eliza faces her own troubles in the French court of Louis XIV at Versailles.
Humans are making enormous progress against global poverty and diseases, we’re living longer, more children are going to school. You name the area of concern (except global warming) and we’re improving. That’s been the case since roughly the end of the Second World War. Perhaps it isn’t so evident in the ‘West.’ But most people don’t live in the ‘West’ anyway.