May I ask which part is a waste of time?

You can ask. Hard to answer.

I happened to study for one year in the philosophy department at Hebrew University, and also got to know some of the key people there. Maybe I can shed light on a few points (although I myself don’t know enough):
A. At least at Hebrew University, a lot of the focus at the beginning is not just familiarity with topics in philosophy but developing “philosophical skill” — that is, the ability to sharply formulate the argument and the claims in what you read and the reasons for them, and to form your own view about them. It’s more complicated than it sounds and requires quite a bit of practice. Even when you study, say, a Socratic dialogue, the focus will be on properly understanding two or three central arguments in the text, breaking them down into a deductive argument that is logically valid, and understanding precisely what Plato’s reasons are for his claims. Again, it’s harder than it sounds. It’s much easier to develop this skill at a university, when you get frequent feedback from people who are really good at it. (If you want to get a sense of the skill level of the people at Hebrew University, you’re welcome to watch David Enoch in discussion with the Rabbi; in my opinion you notice pretty quickly the impressive philosophical precision.)
B. There is a big gap between different areas within philosophy in terms of their value. For example, courses in analytic philosophy, in my opinion, have far greater value. And later on as a researcher you’ll be occupied with “doing philosophy” yourself, as opposed to other areas (various Continental ones), which in my opinion are less important, and where as a researcher you’ll mainly be occupied with “research on the thought of X.”
C. In order to complete the credit quota you need for a degree in the humanities, you’ll almost inevitably have to take quite a few unimportant courses that won’t interest you or benefit you at all. Maybe that’s part of the waste of time the Rabbi meant.
D. It may very well be that there are differences between universities — that is, there are universities where the focus is more existentialist, or less on building philosophical skill and more on becoming familiar with more and more philosophical texts. In my personal opinion, it’s best to stay away from those.

Hope I helped a bit. Take it all with a grain of salt.