I noticed a huge performance issue using the latest version 9.0.2 on Windows 11. The issue is mostly focused on the schematic editor. If I place a big symbol such as the Atmega2560 with many pins and try to moveit, it starts jerking and sometimes it crashes. The same schematic works well on Windows 10 with the same version of KiCad.
I also have this issue on my work PC which has also Windows 11 installed.
My desktop and laptop both run windows 11 and Kicad 9.0.2 and I don’t experience any issues even with large schematics.
I just added a 2560 to an already relatively big (500+ components) schematic and still had no problems.
As gmc mentioned, make sure all your drivers are up to date.