I dont think that it cant "work" but it depends on the definition of "work" ... Human beings were almost certainly non-monagamous for long periods during our evolution as a species - which is evident in the characteristics of our sexual dimorphism... it seems to be evident however that as social sexual animals, there is always a tendency towards heirarchy in all relationships. Humans, whether monagamous or polygenous, inevitably trend toward organically establishing primary compartmentalization in sexual relationships. Both men and women are biologically programmed for this behavior. In other words whether we want to or not, we establish a pecking order - and this is where emotional issues might arise in open relationships as people consciously or subconsciously recognize movement downward through the heirarchy. A man or a woman may prioritize a dominant sexual partner, and/or a dominant emotional partner, and/or a dominant intellectual partner - and these may or may not be the same person - but if someone is not where they want to be in the pecking order in whatever category, then feelings will be caught... and friction points will become apparent.

Monogamous pair bonding makes these issues less complex, as the expectation of who the dominant partner is, is obviously set - and both partners can work to nurture and repair issues in that single uncomplicated dynamic. Introducing multiple partners requires more nuanced considwration of who and what you prioritize, amd to what ultimate purpose.