I’ll go to the mat arguing that Slack is better-designed and better-implemented than Microsoft Teams. But to make a very broad analogy, I think Slack is to Teams today where Mac OS was to Windows in the mid-1990s: better designed, for sure, but not in a way that makes a difference to the corporate IT decision makers and bean counters who are making the call on which platform to use.
Daring Fireball: Was Salesforce’s Acquisition of Slack a Bust?
I love Slack. I’m a Slack Enterprise Grid admin, for goodness sake! But Teams is good enough for most people and already included in the O365 subscription that lots of big (and small) companies are already paying for.
You can say lots of glowing things about Slack, but it certainly isn’t cheap. It is tough to win the argument that “I know we’re already paying for Teams but hear me out. We could continue to pay for Teams AND pay a lot more for Slack!”