The Problem
After upgrading from Windows 10 to Windows 11 the File Explorer takes a very long time to open, sometimes up to a minute.
The Solution
The solution that worked for me was to delete all the files in the following directory:
%AppData%\Microsoft\Windows\Recent\AutomaticDestinations
I believe the files stored in this location are "jump list" files used by Windows to allow you quick access to files from applications pinned to the task bar. By to right-clicking an application icon pinned to your taskbar you get a pop-up menu providing quick access to recent, pinned, or frequently-accessed files. The jump lists are essentially the data that make this possible.