I don't mind both, but don't get why should I use Slack/Teams (without Active Directory integration) when for example Telegram added nice group management into the messenger? More feature rich then both of these, suitable for teams. Ah, no group/video calls... But in case they add group calls - the app will become pretty good for even office communication.
You could already do that in MSN Messenger like, 15 or 20 years ago.
Well Teams is not a direct descendant of Messenger, so it's not like they broke that function. For me that's not a good point.
But, for the record it doesn't work for me either.