> Skype is still relevant to me in 2018 because their core streaming tech is in my experience still more stable/reliable than Hangouts/FaceTime/Slack etc. Often Skype still connects on a crappy network when these other apps fail.

Wait what? I have, at least for personal communications, the exact opposite experience. Skype video often cuts out and pauses, or even entirely drops the connection, at which point me and my friend(s) either switch over to FaceTime (if they have iDevices as well, since its by far the most reliable in my experience) or WhatsApp video (decently reliable and pretty much everyone has it).