It is a common comment on HN to say Teams is rubbish and also to ask why anyone would use it. Now we have a problem of market dominance, which demonstrates by how far the HN bubble misunderstands how ordinary people do their day to day business. This is the vacuum MS have been consistently winning in for several decades now, it would be worth you understanding it.

Now someone is about to reply that market dominance doesn't mean your app is best. If you think that in this case then you are still missing the lesson. Teams integrates with Windows OS, Azure AD, SharePoint, OneDrive, PowerPoint and Outlook in a way that is so much more useful to ordinary people than anything the other messengers do. Much of that integration is available to any app developer but they choose not to use them so continue to fall behind. Sure there will be some things Slack are not currently getting an API for, but so so much more that they don't use but could, because they don't see why it is important for users.