He was not arguing that this is intrinsically better. He was arguing that worse-is-better spreads, the way viruses spread.
Someone else above made the point that worse-is-better was quite reasonable in the 1970s and 1980s when computers were extremely slow and people were willing to sacrifice stability for speed. (Lisp machines, I believe, literally took all morning to boot; and garbage collection was time for a coffee break. At the other extreme, completely unprotected operating systems like CP/M and MS-DOS, that let programmers do pretty much anything they liked, managed to have useful applications like WordStar that were as smooth and interactive as today's word processors. Unix machines lay somewhere in the middle.)
Also, programming was an arcane art and OS designers were willing to trust application designers to "do the right thing" (and if they didn't, the consequences were immediately noticeable).
Today's computers are a few orders of magnitude faster, but are still running operating systems built on assumptions that ceased to be valid nearly two decades ago.