I'm working my way through this change, too, hunting down all the places I've modified org-structure-template-alist. You'll need to get rid of the templates you've added to this list. The new function won't run if it finds an old-style template on the list.
Once the list is clean, the new function offers the possibility of selecting some text, then hitting C-c C-, and choosing a structure that encloses the selected text. This is quite handy.
I had a number of one-line templates that I haven't figured out how to replace yet. Any suggestions are welcome.