No doubt I'm picking an easy target here, but it takes like 700 ms to switch back and forth from the Chat tab to the Calendar tab in the Teams desktop client on my boring work-issued laptop (i.e. commodity hardware). This is repeatable, first time, every time. It doesn't even bother to animate anything or give feedback that a UI interaction has occurred until 500+ ms after the click.

Some things do run very quickly, for sure, but so many of the high touch pieces of code out there from big name corps have some of the worst performance. Hundreds of millions of people use Teams, and many of them use it a lot throughout the day. You must just be getting lucky in what apps you use on a regular basis.