You make a good point about types of matrices that a graph representation makes sense with but it seems a bit much to say that PCA is pseudoscience? If you had

You make a good point about types of matrices that a graph representation makes sense with but it seems a bit much to say that PCA is pseudoscience? If you had a lot of people and a lot of stocks, a low-rank representation of the matrix (probably not PCA per se with that particular matrix, but something closely related) could convey a lot of information about, e.g., submarkets and how they're valuated together. Or not, depending on how those prices covary over time.