So much.
- Window Management, especially fullscreen
- Alt Tabbing Behaviour
- Default Keyboard Layout
- The Dock with its forced defaults (Finder leftmost, Trash rightmost etc)
- No volume control over HDMI
- Power Management (no manual hibernate, closing lid always sleeps)
- File System Support
- The reactions that auto trigger on webcam
- The Global Menu
- Unchangable limit to virtual desktops
- Default apps being hard to change in some cases (mailto: links for example)
- The weird software installation process with dragging icons to a special folder
- That I can't temporarily disable a system management profile
- The way the BSD tools are slightly different than the GNU ones, with grep slower for certain patterns
- No Package Manager by default (unless you count the App store with forced accounts)
- Weird filesystem setup, far from FHS
I have installed various pieces of third party software to fix some of them, but still, those are things I dislike about macOS.