Am I the only one that Hates the idea of open relationships? (But doesn't judge others for it)

with so many sexual orientations and relationship types, it's hard to keep track of thing.. let alone have an opinion on them.. and as for open relationships, they are supposed to work when both parties don't mean to fall/soften for the other party.. which is very rarely the case.. so to get into open relationships, is just stupid when you already know how the other person is..