I'll give my own interpretation. Not that I love Teams, but the alternative in a dinosaur corporation is basically email.
1) WebEx and the open source chat that Oracle appropriated. Fortunately Zoom came and went too quickly.
2) Searching the Exchange corporate directory. BASIC features: status, embedding pictures, attaching files that Outlook would block. Sharing links that aren't obfuscated.
3) Can you even run Teams from Apple / Linux?
4) Ha! Imagine the nightmares for the person linking Atlassian and Teams.
5) Group texts, file shares, voice calls, recorded meetings. Meetings with groups from other companies is almost painless.