Ah, I wasn't clear; I was referring to the modern usage which seem to mean "a thing that I see problems with". I'm unfamiliar with the original definition and have never heard it colloquially, so I'm not sure how it's used.
This is an old discussion now, so I won't post too much more here, but in responding to this, I decided to do a bit of research on "problematic", and it seems (from Merriam Webster) that the first use was in 1609, and was indeed exactly the sense we use it today: "posing a problem: difficult to resolve or decide". https://www.merriam-webster.com/dictionary/problematic
So let's say Umberto Eco's use of problematic was indeed in this sense (as I haven't heard a very compelling alternative). My point is that _he_ could replace problematic with what he's really trying to say, but of course I can't because I'm not the speaker and I don't know what he means. But I can take a few (bad) guesses:
1) The public's music taste is a problem for him because they don't appreciate the aspects of music that he thinks are most valuable. In this case, the phrase would be "congenial to the unsophisticated taste of the public".
2) The public's taste could be a problem because they want easy, convenient access to music via radio and TV, and Eco believes the true value of music can only be expressed live, where the listener has more agency. The phrase here would be "congenial to the convenience the public demands".
3) Maybe the public just doesn't like classical music, and like rock instead. Maybe ""congenial to the modern music taste of the public" would work here.
I could go on and on: the point is, if this were written instead of spoken, and I were the editor, and circle the work "problematic" in red and write in the margin "What are you really trying to convey here?" It would then be a discussion point with the author to dig into the real point so it could be conveyed clearly. But this is an (translated?) interview, so I don't think that bar is appropriate, but I still think there's ambiguity.