Outlook for Mac CardDAV and CalDAV
Unlike Outlook for Windows, neither Outlook:Mac 2011 nor Outlook:Mac 2016 support plug-ins.  The closest thing that Outlook:Mac supports is AppleScript, which won't get you to the CardDAV or CalDAV support that you desire.

For my personal usage, I use a combination of Apple Mail (IMAP), BusyCal (CalDAV, which covers both calendar and tasks), and Apple Contacts (CardDAV) in place of Outlook.  I'm not really happy with this combination.  I haven't found a better solution.