I don't see why our preferences can't be expressed by a utility function even as they are. The only reason it wouldn't work out is if there were circular preferences, and I don't think most peoples preferences would work out to be truly circular if they were to think about the specific occurrence and decide what they really preferred.

Though mapping out which outcomes are more preferred than others is not enough to assign them an actual utility, you'd somehow have to guess how much more preferable one outcome is to another quantitatively.But even then I think most people could if they thought about it enough. The problem is that our utility functions are complex and we don't really know what they are, not that they don't exist.