Austen creates a vivid picture of the world she lived in. The endings are a letdown, but the journey and the plot points have the power to inspire the imagination. Her characters seem almost real and the friendships between women are enough to keep me reading even if the story runs dry.
Regarding the language use, sometimes it is just out of sync with the modern content (“formed an attachment”), sometimes the meaning has changed quite a lot over time (“penetration” “ejaculation”) and sometimes it is all too revealing (“she was his object”). It is still readable without much effort.
If I had to do an adaptation I would set it in a dystopic world with many explosions and gun fights in between the actual plot, just to horrify the Austen fans I know in real life. The sexuality switching would be icing on the cake.