Teams is not a replacement of SFB but a performance-hungry, battery-killing, unusably slow and overloaded poor mash-up of Skype, SharePoint and Mail in an attempt to beat Slack.
Not too hard to beat Slack's user experience though.
Beside Discord, everything else is pretty bad compared to Slack. Microsft and Google failed to deliver anything usable for the last 10 years.
Discord and VSCode really seem to prove that there can be good Electron apps. These apps are great, and take advantage of the perks of web technologies.
Now when I look at Slack or Atom...
Matrix.org has some interesting new ideas beyond slack