But you haven't exactly nailed what it is that we are using as a basis of comparison, despite the otherwise excellent discussion.

And that matters.

Because depending on what criteria we use, metacultural tolerance culture may or may not score highly. Indeed, I suspect that your twin threats of collapse to simplicity or fissioning out of control are areas in which a metacultural tolerance may score quite poorly.

What is the point of culture anyway? Why care if there is social facility, how much context there is?

The answer is that we are social beings, and as such our well-being and happiness depend a great deal upon knowing where in the social webbing we are (especially if there is a strong hierarchy--you really don't want to get that wrong). It's not for its own sake; you actually live a better life if you live the life that comports well with the lives of those around you. Culture is a major way to organize that.

However, by taking it back to the well-being of the members of society, we suddenly gain great discriminatory power between various cultures. Those were large numbers of people are fearful or miserable have some explaining to do: what good are they accomplishing for their members that justifies this degree of harm?

You can then genuinely at least attempt to assess whether a culture that fails to provide robustly for the development of the next generation is meeting its obligations to the members of its society. If it oppresses people of one gender, or one caste, or one race (especially if present in non-negligible numbers), or one height, or one wealth, or one religion, it is very clear that this is a serious negative for the oppressed class so one had better point to correspondingly big positives overall to even deserve a seat at the "this culture should be considered" table.