I agree.
What do all the teams that managed to make it to the Conference Finals have in common?
They have a core group of players that has not changed over the past 2 years.
The Knicks cannot say that, and until they give their team more than a year to figure things out, they'll always be a first-round exit. When it comes to the playoffs, continuity in terms of roster and coaching is just as important as talent level.
I would rather have Nash than Lin at this point, but I do not think that is a realistic idea. Nash is by far the better player - his shortcomings on defense compared to Lin's are not as alarming as the fact that he is a far far better offensive player than Jeremy Lin will ever be. Jeremy Lin cannot run an offense like Nash does. Jeremy Lin cannot shoot like Nash does. Nash is both the best passer and the best shooter in the NBA today, and he has also conditioned his body extremely well. I bet he'll play for another 4 years.
That being said, as much as I like Nash, I do not think that his style of play would fit with Carmelo's.