I don't have first hand knowledge of the OP's situation
So I can't say,
However it is perfectly reasonable to only be open to people who are willing to spend time all together. In fact all of the practicing "poly" people that I know have fairly close relationships with their partner's lovers.
Where it gets unreasonable is to try and force close friendships, or force sex to happen in threesomes.
I know plenty of married people who are non-monogamous, but do not live separate lives. Because they do some much together, which is of course their choice, because they spend so little time apart, neither of them would ever be able to have a healthy relationship as any sort of a hinge. The only way for that to happen is where the two metamours may not be involved with each other, but because they are always in each other's presence it is necessary they tolerate each other.
There are certainly many ways that the situation could be worked, manipulated by a couple which would very much be abuse, however the mere use of words like "US" does not mean anything.
It doesn't mean they feel entitled to anything, it doesn't mean they abusive or blind to said abuse. Anytime a relationship ends people are going to be hurt, and not talk about their lovers in flattering ways, but that doesn't automatically put married people in a box anywhere but here in the poly unicorn haters club.
The might not ever have their triad, and if they ever do, yes it will likely be much different than what they imagined, but just because a married couple isn't exclusive, doesn't mean the must form no metamour contact vees, or else be labeled as abusive unicorn hunters.
I can understand when it's personal and people get over protective of the friends (and for good reason, I would do the same things for my friends if they were treated in abusive ways) but I think it's mistake to brand all non-monogamous married couples as having flawed viewpoints or that they must be oblivious to their abusive behavior
I tried to PM you Jetta, but you have this site's messages capabilities turned off. I hope it wasn't because you were getting nasty accusatory emails, and if you did, they are only pointing out how easy it is to inadvertently treat the third in ways that are abusive, that you really must be extremely self aware to avoid it. The second you let your guard down and begin looking at the dynamic as US and her, it is damn near inevitable to slip into a dynamic that isn't healthy for the third person in your relationship.
And using language such as "she wouldn't talk to US" is a common language used by people who exhibit the "couples privilege" they are speaking of, which usually leads to a devastated woman being dropped from the couple's lives at the drop of a hat.
What they are saying is that it is much more likely to you'll find other people whom you can date separately.
But there too, fifteen years ago doing that was frowned upon almost as viciously, except they weren't called unicorns hunters and it wasn't the couple who were villianized, it was the unicorn, but back then they called them cowboys and cowgirls.
Sometimes trends are inevitable, and interesting enough, cyclic
Hang in there Jetta, you are obviously hurting. Remember non of you is enjoying these stressful times, be patient with other, and listen to each other, if you honestly have drastically different views, it doesn't matter who is right or wrong or if anyone is being more unreasonable than the other, if how you feel, and everyone here could agree or disagree with you and it wouldn't make things any better.
If you care about each other, you will realize you are hurting each other and see that if you cannot stop yourselves from engaging in that, you need to go your separate ways