Don't get me wrong. I don't think estrangement is a good thing. I do think that in many cases it's the last resort after all other options have been exhausted.
I am a member of other boards where people discuss problems with ILs and family of origin. Very rarely is the advice given to CO entirely, unless there are substantial issues (abuse, substance abuse, grandparents who have demonstrated repeatedly that they will not listen to boundaries, etc.). Sometimes we may suggest that people take a break, but not usually a permanent one. The goal is not necessarily to "punish" but to give the person a chance to decrease stress and see if they can think of a solution.
Sadly, too, some people refuse to accept their children's boundaries. They insist on showing up unannounced or sending things through the mail when they've been told not to do so. Then they complain when their children call the police or contact a lawyer. Realistically, do you think brow-beating them into submission is likely to be effective? All this does is prolong the estrangement. At the most, I could see sending a short note or text that just says, "I respect your choice. Just wanted to let you know that I got your message and will abide by your wishes. This will be the last time I contact you; I'm leaving the ball in your court and the door is always open." After that, wait until they're ready.
Is estrangement sad? Absolutely. But giving it constant headspace and dwelling on nothing else isn't healthy. This is why I applaud grandparents who say "We are estranged, it's sad, we wish it could be better, but we have accepted it and are finding other things to occupy our lives." Sadly, I have heard of people (again, not necessarily here) saying things such as "You're killing your (insert relative here), they now have high blood pressure/insomnia/depression/insert health issue here and it's all down to the estrangement."
I admit this may have jaded my views simply because it's what I read frequently. I do recognise that situations can differ.