From the article:

I've tried to answer this question as the conjunction of four concerns:

    What should every student know to get a good job?
    What should every student know to maintain lifelong employment?
    What should every student know to enter graduate school?
    What should every student know to benefit society?

For all the four points listed the attitude of focusing on some checklist covering everything is not really the optimal strategy. For graduate school you may need to pass some broad exam, but afterwards in turning towards research you also want to be much more picky about what you choose to learn and stick to learning mainly (but not necessarily exclusively) things that are likely to help your particular goals.

You should think of learning as of investing and learn things that you are likely to have some use for in the future or ones that you simply like learning. Things that you learn but that you have no long term use for or passion for you will promptly almost completely forget and the time and effort you spent learning them will simply be lost.