I also studied at University of Belgrano and it is a joke.
Well, I went to Belgrano for undergrad and to Harvard for grad school, so I would say perhaps it's not that bad.
I did also go to UBA, and in my experience many of the professors (at least in my field) taught at both UBA and private universities, and the exact same curriculum in fact. The only difference I saw between UBA and private universities was the student-faculty ratio. At UBA, you'll be taught by a leading scholar in a class with 100 other people. At a private university, you'll have the same class taught by the same scholar but the class size will be 20.
Of course, not everyone can afford a private university (even if they are affordable by US standards, or at least they were 15 years ago), so I think it is amazing that we have something like UBA where literally anyone regardless of their background or current circumstances can have direct access to quality higher education. The UBA model is far from perfect, but the social benefits created by the fact that anyone who wishes to e.g. be a doctor can just sign up, go to class, and become a doctor (and not worry about student loans or any of that sh*t) are so great that it is a model worth supporting.
That said, and this is just my personal opinion, from an international perspective although I think the level of Argentinean professionals is very high, the level of Argentinean universities (be it UBA, San Andrés, Di Tella, or any other) is average-to-low. The curricula are antiquated, methodology is nonexistent or lecture-style at best, and teaching is very test-oriented. So we have below-average schools but above-average professionals, which probably means much of the learning occurs in non-instructional environments.
This may stem from the fact that most students in Argentina tend to work while going to school, since professional experience is highly valued here (perhaps even more so than the actual degree). In this sense, I think Argentinean students have a much more holistic learning experience and people are wrongly associating the outcome with the school they went to, when their learning extends far beyond the classroom.