To sync your Outlook address book and agenda with that on your iPhone, you unfortunately have no other choice but to downgrade from Office 2016 to Office 2013.
Fortunately, it takes less 5 minutes and is fairly painless if you have an Office 365 subscription. Thank you, Microsoft!
There are probably (1) no users of Macs + Windows Phones, (2) very few users of PCs + Windows Phones, (3) quite a few users of Macs + iPhones, but (4) many users of PCs + iPhones.
This fourth and largest segment being by far the most important, Apple should update A.S.A.P. its iCloud (currently version 5.0) for it to be compatible with Office 2016!
Update: Finally, iCloud 5.1 is compatible with Office 2016…