Thallo hit the nail on the head; on these topics, opinions can be expressed from various points of view, which I summarize as follows:
- performer
- composer
- musicologist
- listener
Among the 4, I believe that the listener moves more according to taste; I am certain that Frank the listener prefers listening to Shostakovich over Stockhausen and certainly over Webern (except for the Passacaglia), so showing interest in a composer's work is one thing, and the pleasure of listening to their work is another.
Perhaps I am starting from the assumption that my own listening tastes are not interesting, so I am expressing more of a technical opinion as a composer, enriched by some musicological knowledge.
What I want to say is that if a composer, not by choice (see Webern), becomes a starting point and even creates a mainstreaming or is always chosen by performers (for a thousand reasons), their greatness is undeniable. This does not mean that the listener does not matter—on the contrary—but it is easier to fall into matters of taste and lose a certain objectivity. In short, reading the writings, I often cannot discern whether opinions are from a listener or technical in a broad sense. When the two things are mixed, it almost seems as if musicology is at the service of taste. But we all know that is not the case.
In fact, the premise of the topic was modified along the way (I acknowledge this to Daniele); I have truly appreciated and approve of the comments that have been posted so far. In fact, I would like to reassure Daniele or others interested in the discussion... I like to think that it is possible to distinguish the value of Chopin's music compared to that of the last of the composers (I could be the first on this list). Therefore, it is not true that in the end taste guides evaluations of this type; it is difficult to treat a vast and articulated subject objectively through a few posts and a few lines, and so it may seem that taste wins. Or rather, returning to the discussion: someone chooses the points of reference and the starting points; it is, in a broad sense, the taste of many professionals... certainly not just one.
I am realizing that I am getting bogged down in a very large discussion; one can try to put ideas on the table... but the substance is that Bach did not become Bach by chance... the same goes for the others.