Games, though it's more of a game company issue. I like Apex Legends.

Microsoft Office stuff. Every now and then I need to make a presentation, and LibreOffice Impress to Microsoft PowerPoint isn't that good. I resort to Google Slides for now.

Cursor trails. I tried making it myself until I stumbled on the concept of hardware cursor. I still want to do it, but man, putting an image where your pointer is at is harder than I thought. So much more if you're on Wayland apparently.

(Lack of) general ecosystem fragmentation. I still don't understand why I can't paste image that is clearly present in both xclip and wl-paste over Remmina. It does work if I open LibreOffice Draw, paste it there, then copy it back, and paste it in Remmina. Emacs on Xorg is blurry and requires xwayland-satellite but smooth, and Emacs GTK is sharp but stuttery.