My biggest problem with 4k and ultra wide monitors is screen sharing (like on zoom/teams/WebEx etc).

Most people still have 1080p screens at best, so when someone with a 4k or ultra wide shares their screen, it's really tough to see what's going on.

My main display is a 4k TV, but if I have to share, I'm sharing a window, or one of my auxiliary (1080p) screens.