Heterosexuality is not sustainable by red pill logic.

Being straight isn't the most sustainable system if you go by their worldview.

1. They claim feminism ruined relationships in the West.
2. Feminists advocated for women being able to vote, own property, work, and own land. It gave women more options.
3. They're basically saying heterosexuality only works (keeps marriage and families intact) when women are limited and don't have the same level of freedom men have.
4. It's human nature to crave freedom. Everyone wants more options. There will always be tension between men and women when men can do things that women can't do because women are human. It's human nature to not want to be left out.
5. So feminism makes men unhappy, and not having freedom makes women unhappy. Someone is resentful either way.

So yeah, their own logic seems to point to the conclusion that heterosexuality isn't sustainable or optimal on a large scale.