McAfee is known to not uninstall all of its files when using its uninstaller and will not remove them by dragging the application to the trash. That is one of the reasons why it is never recommended to install it in the first place. It is not a bug in the OS, it is the tactics of a malicious piece of software that does not want you to completely remove it from your computer. That way it can scare you into thinking you have a problem so you will install it again.
To help you find the files that are remaining on your computer you should post the free EtreCheck report using the Additional Text option when posting. The report contains no personal information, but will show the McAfee files that are launching on startup.
How to use the Add Text Feature When Post… - Apple Community