Slack is at once a poor communication product, and a beacon of excellence in comparison to MS Teams. It says much that I'd rather use Slack than MS Teams. The bar was low, but by god did they limbo under it somehow.

Basic UX like it being clear when I'm replying to a message or starting a thread are fantastically broken. It's clunky, buggy, slow. It's just a shit-show in every respect. Normally I respect people's preferences, but your preference is wrong.