In the abstract, I really like the idea of having an open hub with individual entrances to the worlds. However, I believe that for it to work, two things are required:
1) The worlds need to be big and in the spirit of Magic Kingdom lands where each one has enough variety in attractions to entertain guests of all ages, and there are enough things to do that you can remain engaged in the world for multiple hours at a time.
2) They need ample turnstiles at each world and a convenient admission system. I actually think that something like magic bands would work really well for implementing a park layout like this. I have never believed that facial recognition is the answer to controlling admission, because it can't be made to work any faster or easier than a simple ticket or magic bands.
The problem, of course, is that Universal doesn't seem to be doing either of these things, so I'm not surprised that the idea has been abandoned.