I was at a concert the other day which had several pieces of late 19th/ early 20th English music by Elgar, Vaughan Williams and Finzi - and the overall impression was of a musical tradition going nowhere - and (in my judgement) that is exactly where it went since I regard the European tradition of classical music as a closed canon.
The sounds were pleasing, and there were some nice effects. But the structure of the music had become a matter of pattern-making without forward dynamics - the music (at this point in history) had become a matter of small phrases (not melodies) which were passed through the sections of the orchestra, the voices or registers - up and down, through various keys - deftly done but why?
Bernard Shaw memorably said that an artists style was effectiveness of assertion and that was it. And attempting to focus on style in and for itself was trivial- yet this is a particular danger for music because it is hard of impossible to say in words what is being asserted - what is the meaning of music.
Yet the meaningfulness of music is vital to its artistic status. Of course it is good to have music that is pleasant, or exciting, of evokes a mood - but it is not enough to constitute an artistic tradition. Properly (in my opinion!) the canon of an art goes between the meaningful artists - those whose mastery is of meaning not style.
The reason Beethoven is so much greater than Brahms is not so much a matter of technical pioneering but that Beethoven had - perhaps above all others except Bach and Mozart - a great soul, so much to 'say' in his music, so much struggling for expression and being expressed.Whereas Brahms simply did not, and his music cannot escape from a core flaccidity.
From this perspective I would rank (for example) Michael Tippet far above Benjamin Britten because (in his early works, only) Tippet was saying something - whereas Britten had nothing to say - or at least nothing interesting. Britten was simply a shallow man of great musical ability. Tippet was a throwback to the late 19th century.
This effectiveness of assertion is ultimately what gives music its forward impulsion. Lacking which a certain stagnant quality cannot be concealed. This differentiates - say - Richard Strauss from Mahler. For all his great qualities Mahler is stagnant, torpid; for all his vulgarities, Strauss was dynamic, energizing. And all who came after Strauss have either been less great musicians, or else tended towards stasis.
Indeed, I would regard the two supposed geniuses of twentieth century music - Schoenberg and Stravinsky - as knowing perfectly well that they had nothing to say, and knowing perfectly well their inability to escape the centripetal pull of stasis - but faking-it, disguising the fact, by explicit experimentalism.
This matter of 'having something to say' is the most subtle and in that sense subjective matter of judgement. And hearing a poor piece by a great composer can be deceptive - in most of what he wrote, Mozart had nothing to say, but was just making patterns of sound on autopilot - and the same applies to pretty much everybody.
One can only judge artists by their best work - and greatness of artistic status requires several great works or at least one very big great work (big to prove that it wasn't just a lucky fluke).
And, at the bottom line, if I personally cannot perceive the artist has something to say, then I cannot, will not, and should not grant them greatness - this is not something that generally ought to be taken on trust from other people.
Especially since most musicians are so shallow! - and this equally applies to critics and scholars. But what applies to music also applies to poetry, drama, novels... all arts.
And it is to be able and adept to perceive and to evaluate meaning of expression for oneself, that one explores and learns an artistic tradition.