Having worked with DC, Marc21 and some of its precursors, I feel that one major problem with the approach is that cataloguers try to infinitely cut up metadata

Having worked with DC, Marc21 and some of its precursors, I feel that one major problem with the approach is that cataloguers try to infinitely cut up metadata into ever smaller pieces until you end up with a impossible large collection of fields with an overly high level of specificity and low level of applicability. For example, the middle name of a married name of a person that contributed to one part of one edition of the work in a certain capacity etc. You end up with so much unwieldily specific metadata that consistent cataloguing and detailed searching become nigh impossible. Ever since search engines, the world has moved into using mostly flat search engines rather than a highly specific facet search for deep fields. Of course, one would want something a bit smarter than full text search, but the real, human world is so complex that trying to categorise any data point quickly becomes an exercise in futility.