The RefToolbar has a feature to fetch information about a citation URL (that feature is disabled when we enable the "enhanced editing toolbar" preference in Editing).
VisualEditor should include that feature to make it as easy as possible to add citations.
In most cases, it's difficult to grab anything more than the page title. But that alone is already great as it is sometimes necessary to look at the page source to copy the page title, which most users won't do. The date, by example, while more difficult to grab automatically, is much more easier to copy and paste or retype for the user.