Mine is that the useState hook is an actual plague on the entire React ecosystem. Regardless of your opinions of React, if you wanna use something then use it right.
Teams is a huge piece of shit.
Why is every meeting its own chat? With no threads! Why are the team channels like fucking forums instead of chats? Why do I get notified between 0 and 4 times for the same message?
I hate teams. I have never had a memorable problem with slack. Maybe some things can be fixed with better use behavior, but good software guides users away from bad patterns.