It took me a long time to realize that Kill Bill is a rampage happening through a movie theater.  Each of the DIVAS has basically gone into a different movie (as if they are actors), and the Bride is jumping from screen to screen-- and basically every genre-- in order to track them down and kill them.

The thing you bring up about directors getting further away from the things that got them noticed, when they were unknown they had little resources to make their flicks, ergo they had to rely more strongly on certain things like heavy dialogue and so on than they do now that they have budgets.  I certainly don't think Tarantino has slipped at all-- in fact, Kill Bill seems like the first movie in a series that seems like the thing he was BORN to make.  At least, that's how I see it.