I would agree that it would be virtually impossible for any other Republican to carry New York. But Trump has a very considerable advantage over other Republicans there, because of his unique position in New York; because of his celebrity status; because he is one of them--really one of them, not a corporate manager moved there--and talks to them like someone they know personally.
Hillary on the other hand is a transplant. That does not hurt her in Manhattan-home to the Corporate transplants, etc.; but she will not do as well against Trump in the other boroughs; while she will be taken down, big time, up State.
There aren’t enough Independents in the State of New York to out weigh the votes that Hillary and Sanders won in the election. Sanders won 200,000 more votes than Trump and Trump has just made himself unlikable. Sure, he will win a percentage of the Independents and Sanders voters but not close enough to make a difference.
Now, Trump is moving to the center, abandoning the voters who got him this far. No Trump cannot win anything for real, not in the National election. By November, Trump will have only succeeded in destroying the Republican Party. ...but that seems to be the goal of Trump’s Libertarian backers.