It's not that much about the UI even(which is terrible as a lot of other people here explained), but rather the disgustingly bad performance and costant issues.

It's not that much about the UI even(which is terrible as a lot of other people here explained), but rather the disgustingly bad performance and costant issues. I use teams every day at work, it eats insane amounts of ram, it leaks memory during video conferences, it's practically unusable during a call, switching tabs from chat to teams takes anywhere from one to five seconds, push notifications simply do not work properly, so does motification badge - it also often takes seconds for teams to acknowledge that you've seen certain activity. Text input has such an insane latency that it's uncomfortable to write, often eating characters from the next message after pressing return if you start typing too quickly. And this is just a tip of the iceberg. Almost all of few hundreads of people in our org hate the app as well and we're almost purely a Microsoft shop. I liked Slack until it became incredibly bloated. But even now, it's still in another league when compared to the abysmal experience that Teams offer.