Teams is anything but a basic messaging app. Over the last few years Microshit kept integrating most of their office suit into it instead of keeping their standalone apps working beyond Excel and Word. Now you have chats, teams, calls, calendar, SharePoint, planner, to-do, power BI and a million other things in one place, and only 90% of them don't work properly.

Besides, the new™ Teams is pretty much just an instance of edge with 10+ tabs open den being on the amount of addins your company has. The entire app is literally just build in edge webview, its a reskinned browser with slightly more privileges.