These stories that paint people so stuck in a life they don't want is mostly hogwash. Nobody put a gun to their head and said marry this man or woman. Just because they don't want to choose the life which would make them happier in the long run, is no one's problem but their own. I have no pity for them. You reap what you sow. I'm happy for those who love reading about depressed people, but I choose not to read self pity stories and so will pass on anymore of this one.
Whether or not the actions they take are good or bad can be up for debate, but these are actions real people take to deal with the world around them represented in fiction. What you're saying is something akin to "Hey, why don't atheists just be open about it in the middle ages? Their unhappiness is their own fault, lmao."
It's like telling someone to pull themselves up by the bootstraps when said person has no boots at all from the start.
Yukako's and Chinami's internal circumstances are different. Seems to me, based on her grit she's shown, Chinami has been out first and foremost to herself, it's good. But Yukako doesn't seem to have that self-motivated courage to even admit to herself that she swings that way regardless of how many times she's slept with Chinami; it's a classic "closeted" case. Yukako was seemingly raised or encouraged to be "the dependable one": i.e destined to be a mother and serving her husband. Like, she's been programmed to put others' concerns before hers. Just look at how meek she is compared to Chinami who looks like she can swath away men like how carabaos do with flies.
Nobody put a gun to their head and said marry this man or woman. Just because they don't want to choose the life which would make them happier in the long run, is no one's problem but their own.
As Lucas Magnus has said, it's social suicide to go against the grain.
So, what about now that Yukako's confessed to her "crimes"? Is that not an act of "choosing"?
Yukako telling her husband now that she's in love with someone else doesn't disqualify the fact that the odds were certainly against her before all of this.
She only did so now because one: they are now adults. And two: Chinami backed her into a corner and made Yukako realize that Chinami is the only one who truly loves her. Essentially, Chinami's the "outsider" who reached out and gave Yukako the "boots" she needs.
It's pretty telling how Yukako describes her dreams about her and Chinami. For me, that moment seems to be the signal that she's finally grown the courage to face everything head-on.