Win 10 upgraded to Win11 screwup

I recently upgraded my computer from Windows 10 to Windows 11, and something has gone seriously wrong. The upgrade process seemed to complete without any error messages, but now my system is a complete mess: my taskbar icons are missing or unclickable, the Start menu won't open at all, many of my apps crash immediately when I try to launch them, and the overall performance is painfully slow even though my PC ran perfectly fine on Windows 10. I've already tried running the Windows Update troubleshooter and checking for additional driver updates, but nothing has helped. Has anyone else run into similar problems after upgrading, and is there a way to fix this mess without having to completely wipe my drive and reinstall everything from scratch? I would really appreciate any advice you can offer. Thank you.