Ok, that was sloppy phrasing on my part, but my point still stands: The entire reason that KDFs exist is to deal with the fact that hash functions are designed

Ok, that was sloppy phrasing on my part, but my point still stands: The entire reason that KDFs exist is to deal with the fact that hash functions are designed to be as fast as possible. If it made sense to make hash functions slow, then KDFs would not be needed. While KDFs do use hash functions internally, the hash function is an implementation detail.