Comment by mysterypie

In addition to everything you said, and I would also add:

- Microsoft turned Skype into spyware. Before Microsoft, Skype used encrypted peer-to-peer connections which I'm confident had excellent cryptography given how much it annoyed some governments that Skype couldn't be bugged or monitored.

- Microsoft provides no way to delete chats, voicemails, and video messages, although they give the ridiculous option of "hiding" old conversations as if that's a reasonable substitute for deletion. At this point, it wouldn't be greatly surprising if they record and save all voice calls.

There's inertia in people and companies abandoning Skype because everybody knows it and everyone has it (or had it). But the thing that really preserves Skype is that it can connect from any device to device, including landlines, and it can do all of audio, video, and text.

A Skype-killer product needs (a) to run on all major platforms so you can communicate with someone regardless of whether they are on Windows, OS X, Linux, Android, or iOS, and (b) the ability to make connections to landline phones, (c) do all of audio, video, and text chat, (d) be reliable and trustworthy. That would be the Skype killer.