As others will mention the Cap complication would prevent that trade from happening. Rangers just have too many big salaries.
With that said, I think any team that adds a JT Miller would be getting a really good player. Over the top? Way too hard to call, but better? Yes, way better! The club made it to the ECF and then faded out against a much more playoff experienced team. Miller would have added a lot of depth there. Tough to measure where they could have gone. In the playoffs the kid line developed into a really strong line. Millers last playoff performance he produced PPG. The Rangers top producer didn't produce at the same rate when the games got heavy. His Center (Strome) missed some of the best scoring opportunites the entire playoffs. He ended up with 2 goals, after producing 20 something during the season.
The proposal was Miller for Chytil plus. The Rangers needed Miller for Strome, which would have not worked from a value standpoint, Strome expiring status etc. Rangers had other pieces to add, but again. They were forced to made trades for expiring assets as they were really capped out. Same situation for them this season.
Miller with Panarin would have given the Rangers the Left Handed Center feeding the Right Handed Left wing. Of course theres no idea of knowing if they would have clicked or not.
At the end of the day, what really stings is that the club had him already. They had him as a protected asset along with their captain who was also a protected asset. They traded him, in the worst deal the club made in decades. Makes me angry to even look back at it.