I wouldn't wish Teams on my worst enemy, so in that regard, I love Slack
The thing I struggle with the most is how I'd move all of our core functionality from Slack. A lot of the people/teams that build these "Slack killers" I don't think have ever run Slack at scale
How are you going to replace the 30+ in-house apps I've built that automate 50+ workflows?
How are you going to replace the 100+ workflows I use with 1,000+ clients when they have to submit a ticket, or questionnaire, or a security event?
How are you going to replace the 100+ partner channels I have where we send out automated messages about specials and discounts we're running?
What about the 500+ other apps I run that integrate with our systems? Are they going to support your new platform?
Do you have retention settings? DLP? How granular can I go on permissions? What about picking up events via the API so I can train people in real time on what not to do in public channels?
I have no affinity or personal ties to Slack. But if you're going to position yourself as a Slack competitor you have to actually do what Slack does