Hall of Fame
Not just in matches--on the practice court too. He hasn't added anything to his game, as you say. If he stays one-dimensional like that, his best case is vulturing a Wimbledon or two.This dude hasn't made a QF at a slam in three years now, not even wimby wich he considers to be real tennis. Guy couldn't beat Nishikori.
I think as the years has gone by Kyrgios has gotten worse and worse as a player, wich is very rare to say. He had some game atleast couple of years ago but the last 2 years or something he has turned into Karlovic. Complete servebot who can't do anything on opponents serve.
I suspect it is just lack of work ethic. I really think he lacks the work to fight for every point.