My colleagues and I had set up a nice self-hosted XMPP server which everyone could use to chat in-house without any of the traffic leaving our network. We had it end-to-end encrypted and it was quick and easy. Then management (with the support of a few employees who like hype) switched us to Slack. It wasn't private, it wasn't end-to-end encrypted, all our confidential messages went out to the internet, the boss could technically read anything we wrote, and many people didn't like the UI. Once management got frustrated with Slack they switched us to Microsoft Teams. After using that for a year, I miss Slack. Teams is a bloated buggy mess with a UI designed to confuse and no privacy, and it also has all the disadvantages of Slack.
A few of us have secretly switched to Matrix and Element. It's good. Don't tell management.