I find async conversations quite valuable as well. In the early days of email when it was used as a substitute for post mail, people mainly wrote emails to friends and family. Those letters were usually long and written with care, as if we still thought it was expensive—in terms of money, but mainly time wise—to make those words reach the other end. The relationship was already there, what email provided was a more efficient way to maintain it.
Email is now seen as an obsolete and inefficient way of communication, but I still think it is quite useful as it forces us to slow down a bit.
Today, there are plenty of “real-time” communication channels, the user experience is friction-less. The tools help us to efficiently remove anything that causes the slightest discomfort—such as talking with people who think diametrically different from us. Thus, our ability to have meaningful conversations is eroding as we carefully craft our echo chambers. We have forgotten that those community bonds are not only the result of joyful shared experiences, but also the day-to-day frictions and life-changing conflicts, and our ability to overcome them and stick together.