Misguided_Rooster From a historical perspective, monogamy is trash.
From a literature perspective, it CAN be a useful plot tool. This is particularly so as polygamy was the default for most of human history. Love, admittedly, had little to do with it though as it was primarily for procreation and ensuring the continuation of lineage.
Unfortanately, most authors do not seem to know how to use it. I've read very few harem works where the handling of the harem did not detract from the plot of the story and fewer still where it added value to it. This is the fault of the writers though, not the harem tag.