Which is unfortunate, but a consequence of Microsoft's perennial, embrace, extend, extinguish - they embraced instant-messaging version 3 (or wherever we are now), and they're onto the extend part - extending Teams' reach by bundling it 'for free' in Office, and the OS, so people don't "need" to buy Slack.
Slack won't be 'extinguished' but it will have a falling market share, despite the dumpster fire that is Teams, and the bean-counters in most corporations getting kudos from their bosses for 'cost savings'.