My friends and I only use Discord because Skype devolved into a phenomenally terrible experience after Microsoft acquired it. None of us have pledged allegiance to Discord; there's simply no markedly better option out there.
As far as voice quality goes, or is it all the other, more social, features that are the deciding factor?
Just random examples, but I have experienced better voice quality using Teamspeak, Microsoft Teams, and Telegram (desktop). I have commented on specifics regarding Discord's voice quality previously.