Out-of-context quote. (Even if the original is slightly strangely written.) The "update it" refers to the book The C Programming Language, not to the C language itself; C itself has seen an update as recently as 2011.
It's not out of context at all. It's bizarre to assume that every book ever written about a subject will be updated constantly by it's (currently septagenarian) authors in perpetuity and/or that a failure to update it is an indication of the culture in general and not the authors having literally anything else to do.
It's not like books on C stopped being written by 1990.
Yes, but The C Programming Language is almost always recommended as the book to read.
Still an odd statement, since one of the authors is deceased.
It's fractal.
He means the authors have failed to update the book, The C Programming Language, not C itself.
I would say the authors have failed to ruin a classic by trying to update it. It's short, concise, readable, and useful as a reference. Not sure why anyone would want to mess with it. It was still a fun quip about the age of the language.
In an age when I expect and experience 0.0.X versions of very popular and important Python packages to have major API-breaking changes, it's extremely relevant to point out how a 30-year old, un-updated, book can be useful.
Not just useful, but impressively currently useful. Picking up K&R with little previous experience, and you can make a program that does something in hours, on a current machine. It's dense, but well-written and easy to pick up.