Is attending an academic conference beneficial if you are not presenting any paper? Does it reflect well in your CV?
There is one additional benefit of attending conferences: networking.

Networking works best, of course, if you present a paper, because then you are formally advertising your work and yourself. But whether or not you are presenting, you should spend a lot of time talking to other people, getting to know them and getting them to know you. Spread your contact information and your research interests far and wide.

No, this won't show up in your CV. But knowing people and being known is usually far more important than whether a conference or a conference paper shows up in your CV.

Browse the many questions tagged conference or networking or both for ideas on how to go about this. (Hint: start preparing before the conference, by checking who will present and who you will want to meet. Maybe even contact a few people beforehand and set up meeting.)

Whether this is worth the registration fee (in whatever currency), plus travel time and costs will depend on you, your career plans and how well the conference and its attendees match your interests. I certainly have attended conferences without presenting for networking purposes.