This error message is, most likely, due to System Integrity Protection (SIP) preventing it from being installed in a critical system folder. Disabling SIP would potentially resolve it, but is highly recommended that you don't do so.
SIMBL is not part of macOS, but is an extension that can be used by developers to extend their applications or plug-ins where they may not have access to the original source code. There is an installed app or browser plug-in on your Mac that added this and may be corrupted or missing, thus the error.
Typically, SIMBL, will install itself as a web browser plug-in in either the /Library/Application Support/SIMBL/Plugins or ~/Library/Application Support/SIMBL/Plugins folder. You can use Finder with Go to Folder to find and delete them.