Yeah, we know. Those are not two adjectives that normally describe the same tone. But Thomas Hardy doesn't play by your dang rules. He's a rebel.
So, when the narrator is describing the landscape, he adopts the tone of a passing observer—someone who is interested in what's going on, but not someone who's really invested in any of it:
The club of Marlott alone lived to uphold the local Cerealia. It had walked for hundreds of years, and it walked still. (2.6)
During climactic or very emotional moments, though, he adopts a more sympathetic tone. For the most part, that sympathy is more of a general sympathy—the kind of pity anyone would feel for someone suffering as Tess does. That universal sympathy makes the reader identify even more with Tess.