Too late for what? Some mid first round picks and role players who can barely hang on in the league like Denver did? You don't trade box office guys for garbage.
I could outline all the mid to late first rounders in the league contributing, but I know that wont matter
It's funny you mention Denver, since they actually have a better record since the Melo trade than the Knicks
Too late, as in before you can't get any kind of value for him, last year it was Jimmy Butler & Niko for him, this year it's "Hey, maybe we can get some mid first rounders?". You get value for him while he still has some and accept the reality of the situation which is the Knicks are not going to win a title with Melo, so why exactly hold onto him like he's the difference between winning and losing a ring?
Look at the Grizzlies as an example of a team that didn't know when to move on.