I was so/so on Xia when I played it. It wasn’t a bad game, but it wasn’t anything special. There was no real reason to become a pirate, and most players found one trade route to follow forever.

The expansion, with its changing marketplace values fixed the One Trade Route issue. I’m still not clear if there is any reason to go pirate, but fixing one of the bigger issues is (IMHO) a good excuse for picking up the expansion.