Imo, the new doc are equal to confus that old UDN, a mess of links in the middel of wall texts.
Look one of the more important page about communication between blueprints, the only link to the tutorial about implementing interfaces is in the end of a wall of text.
https://docs.unrealengine/latest/INT/Engine/Blueprints/UserGuide/Types/Interface/index.html
The docs need a lateral tree of content like maya for example:
://download.autodesk/us/maya/2009help/index.html?url=WN_nPart.htm,topicNumber=d0e55367