question

May I ask what part is a waste of time?

It's possible to ask, but it's difficult to answer.

I had the opportunity to study in the Hebrew philosophy department for one year and also get to know the people involved a little. Maybe I can shed some light on a few points (although I don't know enough myself):
A. At least in Hebrew, much of the initial focus is not just getting acquainted with philosophical topics but developing a "philosophical skill", meaning the ability to carefully refine the argument and claims in what you read and the reasons for them, and to formulate your opinion on them. This is 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 understanding two or three central arguments in the text properly, breaking them down into a logically valid deductive argument, and understanding precisely what Plato's reasons for his claims are, and again, it's harder than it sounds. It's much easier to formulate this skill at university when you receive frequent feedback from people who are really good at it. (If you want to be impressed by the guys’ Hebrew skills, you’re welcome to watch David Enoch in a debate with the rabbi. I think you notice the impressive philosophical precision pretty quickly.)
B. There is a big gap between fields within philosophy in terms of their value. Let’s say analytical philosophy courses, in my opinion, have a much higher value, and later on as a researcher you will be busy “doing philosophy” yourself, compared to other fields (continental ones of various kinds) which in my opinion are both less important and as a researcher you will be mainly busy “researching the doctrine of X.”
C. To complete the quota of credits you need for a degree in the humanities, you will almost inevitably have to take several unimportant courses that will not interest you or be of any use to you at all. Perhaps this is part of the waste of time that the rabbi was referring to.
D. There may certainly be a difference between universities, meaning that there are universities that focus more on existentialism, or less on building philosophical skills and a lot of preoccupation with getting to know more and more philosophical texts, in my personal opinion it is recommended to stay away from such.

I hope I helped in some way, take everything with limited liability