Using one partner's friends for reference is an interesting idea, but I think it's wildly unreliable, because opinions are biased and subjective:

- Some friends could be highly demanding, so for them nothing will ever be enough (yeah, imagine how joyful their marriage... ;-).

- Some could be hypocrites and never saying what they're really thinking.

- Some would apply their own standards or needs, that could be far different from our partner's.

- Some could be jealous or envious, hence they would criticize only out of spite.

- Some have a grudge towards the opposite sex (this is widespread on many social media), so anything they say is tinted by their resentment.

And so on...

Yes, one could really find some good hints in their feedback. But how can one know if that feedback is reliable or misleading?

> "But you most certainly should care about what your partner’s peer group considers a good partner to be, because that likely has 99% overlap with what your partner wants"

Only if that partner's group is highly similar to the partner.

Actually many people enjoy "complementary" relationships with people different from them. Thus their friends aren't a "carbon copy" of them.