The one thing I liked about it was the balance of "threaded conversation" and "chat" that it promoted with its UI, which was good for the data science team I was on at the time. Of course nowadays I would suggest using Zulip for the same purpose.
On some mobile apps (Gmail, Discord, Telegram, etc. On Android, never used a modern iOS device to know the situation over there) there are embedded browsers enabled by default, but they are not very persistent and have no actual browsing UI.
My mom was buying something from a link she got from a friend, and was unable to complete the transaction because she had to open another Telegram conversation to get the payment details (hey don't judge non-techy people's organization skills!), but of course going back means leaving the browser-view, so once she had the details at hand she couldn't go back to the store to finish the purchase.
That would be "fine" if there were a consistent UX to "no, i really mean to open this on my browser app, not on an embedded view" or if embedded views were opt-in, but as it stands, it is one of the classic attempts at "simplifying" things that actually makes the whole ecosystem more complex and obscure.
More like a Webex Teams knock-off, as MS went after the Unified Communications space (group chat + video meetings, though they still lack contact center and hybrid meeting hardware).
But it could be that voice/video calls were blocked by our IT because at that time WebEx was our approved tool (not WebEx Teams, just the regular scheduled meeting tool).
It started as a Slack knock-off. Not a great one, the UI is too low density and the multi tenant support sucks unlike Slack's. But it was relatively snappy. And free for O365 users. But lately they've been adding many apps, Wikis, all these fancy meeting modes that make it seem like everyone is in a theatre and many more fluffy things.
Now the app is so slow it takes more than a minute to start up. It often crashes with stupid error messages "Oops! Something went wrong!" that give zero indication of what actually happened.
At the same time MS is heavily pushing companies to adopt it but they're devaluing the product as they go by making it some kind of Swiss army knife with all the trimmings.
They're now realising the performance issue and moving away from Electron towards Edge webview but I think what it really needs is a proper architectural review. They've been too focused on beating the market adding new features and its core functions have suffered.