Massive amounts of telemetry data and nearly every app these days just being a web app just chews through your hardware. We use Teams at work and it’s just god awful. Hell, even steam is a problem. Even having your friends list open can cause a hot to your fps in some games.
When I login to my work laptop in the morning, before even doing anything, Teams is the app using the most resources - typically 300MB-400MB, while doing nothing.