Personally I don't have anything against polyamory. I just don't ever intend to engage in it, because I don't feel that having multiple romantic partners allows one to give the full attention necessary to a healthy relationship.
Eeehhh... thing with a healthy poly relationship is that the group is
sharing attention. Same amount of attentiveness, just split three ways instead of two. Relies on synergy to make up for that somewhat lessened one-to-one concern. It... doesn't work for a lot of people, but it does for some. There's
give with poly relationships, from what I've seen, in terms of what sorts of stresses they can take, that you don't have in couples -- can't, really, due to simple logistics and whatnot. Having three (or more) people to split the burdens of life means no one of them are quite the same degree of linchpin they can be with a single pair... and there's situations/relationships where that can make a lot of difference, just having the extra flexibility on all levels (emotional, physical, fiscal, etc.) that having three people on tap instead of two provides.
Old friend of mine's actually been part of a poly triad for the better part of the last decade or so. Good odds th'fellow wouldn't be
alive today if it wasn't for their support, and it would have been a
lot rougher if it'd just been one partner. But with two other folks able to make time and provide aid (and have time made for, and aid given, etc., etc.) instead of one, well, not able to. It's worked out pretty well, so far as I'm aware.
... personally, it's been a long while I've figured that a polyamorous relationship is probably the only sort of romantic one I could be in that
could be healthy. I just don't have the energy or emotional... consistency, I guess? To really give what's needed to be someone's sole support in that sort of sense. But with another person in the mix to help dilute the effort involved for any one partner a bit... maybe, y'know? Maybe. Probably never get around to trying, but eh.