AFF is very much oriented to swingers and open relationship types, along with a few other things...the environment there is very sex based. There's also a lot of limitations on the site designed to make and keep people paying...so yeah...no one reads profiles since generally they can't see them. The poly's are probably there, but I think many loose interest after a while of dealing with the same issues you mention.
There's other free sites like PlentyofFish and OKCupid. POF is fairly mainstream, but there's probably a slightly higher Poly ratio there. The FSF section also has a fair number of couples seeking unicorns, so you may find some similar situations as AFF...but at least you don't need to pay for it.
Generally OKC seems better recommended, as the matching algorithms while fallible still tend to trickle like minded poly folk to the top of your matches.
Agreed to whomever suggested that dating resources should be made into a sticky thread.