All Icons Are Invisible Until You Hover Over Them

That sounds like a frustrating display or rendering issue. Since restarting Explorer and rebooting didn't help, I'd try updating (or rolling back) your graphics driver, as Start Menu rendering problems are often GPU-related. You can also run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth from an elevated Command Prompt to repair any corrupted system files. If the issue started after a recent Windows update, checking for newer updates—or uninstalling the problematic one if appropriate—may also help. Creating a new user profile is another good way to determine whether the problem is system-wide or limited to your current account. Hopefully one of these steps resolves it without requiring a full Windows reinstall.