“Taking a lot of time” is what’s implied by impossible.
By the time you are done building whatever-it-took-long-time-to-build a new generation of users have just emerged.
Your product is either a) obsolete to the youngest users, or b) you, as the product builder, lost the point of reference of the youngest generation
From the blog:
>I conclude that it is impossible to build a new web browser.
And a new OD. The entire world communicates now by two OSs only..android and iOS.