What do you think adds most to the playing time? AP seems to be not too bad despite the multiple choices. There is a fair bit of bookkeeping at the end of each round though.
Pixie Queen has a few distinct phases during each turn. They all play very distinctively, and most require active decisions (actions, offering, rewards), while others are mostly passive (income, penalties).
Even though it's a worker placement, it's different from Lords of Waterdeep. LoWD is a bare bones worker placement (which I like very much about that game), Pixie Queen does this differently and is a worker placement with bells and whistles.
These extra elements/phases just take time. Each phase plays very differently, and the fact that the gameplay is divided into these three active phases lessens AP. During each phase it's very clear what you should be aiming for.
But yeah, basicly that's the reason for the additional playing time. LoWD has an action phase. This game has an offering phase (blind betting minigame) and a reward phase (spatial movement of pixies) on top of that.