Well, Liyue is much more than "rocks", as you said. It's true that Liyue has many crystals and ores, and they are a big part of what has allowed Liyue to be successful. We exorcists make use of them as a part of our thaumaturgy during exorcisms, for instance. But that's not all that Liyue has to offer. The people are hardworking and dedicated, and the land is full of numerous bounties, and we have a rich history that has defines many of our practices for generations. We may not be known as the lands of freedom in the same way that Mondstadt is, but we are a prosperous and free people in our own right.

[He isn't as good at words and fanciful wordplay as Xingqiu is, but he does his best to describe his homeland in a positive light.]

To put it simply... it's home. And it brings me no greater pride than dedicating myself to protecting Liyue from the evil spirits.