Windows 11 has round corners.

Someone wanted to make it kid-safe. Except they didn't notice that they are designing a software UI and not a wooden cupboard.

This. The best feature ever. Microsoft might not be able to draw shadows, scrollbars, window borders but they sure know how to round corners. Wanna exit word by pressing exit in the menu (i.e. clean exit). No way. You must press the "X" on the upper right window corner and hope that the corners rounding Microsoft engineers handle the "WndClose" message gracefully.