I am in the Diap camp
The truck load of subject tags are holdovers from the paper card catalog era .
Fiction, science fiction, blah blah blah
may have been from an era when you needed
a card in each of those categories.
My town has been using Electronic catalogs since the 1980's ( And now uses the old space for terminals
) I could even do keyword searches back then, who needs 97 (mostly wrong) tags