I wonder what the value proposition is for actors taking on these movies anymore.

A decent pay cheque I imagine. Also, if you've ever dreamed of being able to fly or punch a bad guy through a wall or what have you, you'll be able to live our those fantasies (and getting paid for it). In other words, it might just be a fun experience. Not everything has to be a calculated career move.

Surely she has the pull to land something better right now?

I dunno. House of the Dragon was her big break, no doubt, but she was only in a handful of episodes. She didn't break out in the way that, say, Emilia Clarke did on Game of Thrones.