I have just finished watching the entire 6 part series. Yes the plot in the way it is presented is complex. We are presented with events and then history leading up to that event, more events and the histories leading up to those events, and so on. This makes for a complexity that requires some attention, although many hints are always on screen to tell us where in time each scene is located, past, recent past, and present. The complexity is a positive, but a casual viewer with the show on in the background with sparse attention paid to it will find it hard to follow the twists - you need to actually watch it.
It took me until the 3rd episode (first two with mild attention wandering) before I became absorbed, will probably watch again in a couple of weeks with fresh eyes.
Clever, a slow burn, this show is a bit of a gem. I would summarise it thus:
Gold, greed, gowns (will make sense when watched), love, murder, mystery, mystique and revenge. A healthy dose of good viewing. I was sorry but also sated when it ended.