I guess it depends if you are going for a job that REQUIRES these techniques then yes it is important, but for web application development - even sophisticated web application development - not needed.
You should know a number of things on this list if you do back-end webapp development, particularly for large/hairy enterprise stuff. So maybe you are referring to front-end only.
Almost all of those are handled by a standard library, so why bother.
When issue arises then you look for a book/website and fix the problem.
Source: Doing backend (and some frontend) web stuff for the last 10 years.