I'll grant you that online dating does make the process of finding bisexual+poly+attractive women in your area a lot faster. It still doesn't guarantee you that any particular woman is going to fancy either you or your partner, though, and you are still massively reducing your chances of finding a partner for either of you, if you are still looking for one person to suit both.
Let's say you live in a city with a population over four million, so that at least half of those are women. Bi, poly and attractive-to-you women will make up (probably) around 0.01% of the population - okay, so in a city that huge that's 20000 women, but don't forget that the vast majority of those women will already be dating or married and not available. Let's say 10% of those women are actually looking for someone to date... of those 2000 women, maybe 10% (200) will fancy you, and maybe 10% (20 women) will also fancy your partner. And maybe two of them will be interested in trying out an exclusive triad situation. None of which guarantees that a relationship with either of those two potential women will actually work out, but sure. You found them pretty quickly, and only had to message 2000 women to do it.
OkCupid, or whatever dating site you happen to use, might well make your disappointment happen faster. What it doesn't do is change the odds of what you're looking for actually being available.
Re: One possible solution...
I'll grant you that online dating does make the process of finding bisexual+poly+attractive women in your area a lot faster. It still doesn't guarantee you that any particular woman is going to fancy either you or your partner, though, and you are still massively reducing your chances of finding a partner for either of you, if you are still looking for one person to suit both.
Let's say you live in a city with a population over four million, so that at least half of those are women. Bi, poly and attractive-to-you women will make up (probably) around 0.01% of the population - okay, so in a city that huge that's 20000 women, but don't forget that the vast majority of those women will already be dating or married and not available. Let's say 10% of those women are actually looking for someone to date... of those 2000 women, maybe 10% (200) will fancy you, and maybe 10% (20 women) will also fancy your partner. And maybe two of them will be interested in trying out an exclusive triad situation. None of which guarantees that a relationship with either of those two potential women will actually work out, but sure. You found them pretty quickly, and only had to message 2000 women to do it.
OkCupid, or whatever dating site you happen to use, might well make your disappointment happen faster. What it doesn't do is change the odds of what you're looking for actually being available.
At least that's my take, as a 'unicorn'. ;)