This article explains the huge problems seen at the Freedom Tower construction site:

Of Time and the Freedom Tower

From the article:

The toughest of all ground zero questions is: What’s taking so long? The reason it’s so tough to answer isn’t because there are no answers; it’s tough because none of the dozens of answers is a sound bite, and trying to parse them is like uncrumpling a train wreck.

Here’s what it looks like today:

Here’s what it will look like:

[See previous Doesn't Work]