It has nothing to do about that. It's that Miller isn't on his last year of his contract, Rangers can't afford him next season with zero cap room. They wouldn't have dumped Buchnevich for a terrible exchange if they could afford more top quality in the lineup as it already was. With the raises of Zibanejad, Fox, etc, even Strome will probably be gone next season because of cap issues and he's not expensive. Why trade for a player you can't afford?
And if Vancouver wants prospects already playing in the NYR lineup or some other high value ones and not just picks, well, that's an additional problem. NYR won't win a cup with or without Miller, they still need some years in them.
It was expected among many NYR fans that Drury would only make depth moves and so far that is all he has done and only with middle picks. There is no expensive mercenary on his last months of his contract that fits the role needed in NYR. NYR's problem is depth, not talent because of long term injuries to Blaise (I think, I barely remember his name in the few games he played before Slewban blew out his knee) and Kakko.
The cap of the player going to NYR could be $40 million this season, but has to be $0 next season.