Unfortunately he is right. Many websites are awkward to use, or simply don't deliver for their users. That's why many get few viewings.

Standards for website design

Nielsen's hobbyhorse is usability and standards. Understanding why websites need standards is critical. The easiest way to explain it is to go back to old media. Take a book. A book in the English language, starts on a right-hand page and we read it from the first page to the last. The text runs from left to right. It has a cover with a title, the author's name, and maybe some more information about the contents.

These elements are so obvious to us now that we don't bother to think about them. They are standards and conventions which help us to be able to read the book. We don't need instructions.
Websites should aim to operate in the same way. Why should we need to think what to do when we go to a new website? Why shouldn't there be a menu, a search button, a log-in etc in a position that we understand, and which works in a way we understand?

Website teams

Taking the second part of Nielsen's statement, websites are frequently designed by 'teams' or individuals who can do elements of the job, and fudge the rest. It is the failure of so many so-called web designers to undertstand the specialist nature of the roles involved in constructing a website, that leads to so much poor design.

A website comprises much more than just  graphic design, which is what the naive customer will think it is. There's also list of other activities: programming, content editing, content writing, image creation and optimisation, data management, administration, workflow or information flow. All of these should be co-ordinated by a project manager. If you're not getting this, ask why.