A first performance is, most of the time, merely a try-out, and depending on the work, it can be entirely sufficient ('Ah I hear it... no I would never ever want to hear anything like that again') or opening-up a wish for hearing it again ('Oh this is strange... it affects me although I've no idea why because it's contemporary... I would like to hear more of this'). And anything in between. There is no filtering system that 'garantees' sufficient artistic quality to reassure audiences that its time and patience and goodwill is not wasted. We simply have to hope that both the conductor and the programming staff hit upon something that, at least, will be worth a hearing.
The great difficulty of programming new, unknown works, is that there are no longer any standards of language. So, how could one judge? This is the result of 20C modernism that wanted to liberate serious music from traditional standards. If these standards were suffocating strictures, one could wholeheartedly agree. But there also were standards of artistry, sophistication and expression, which are hard to objecify and depend upon musical understanding, which is a subjective quality. Nowadays, the lack of any standards shows itself to be a great obstacle to ever arrive at the addition of valuable works to the existing repertoire.
On top of this are two painful factors, never talked about publicly but showing itself too clearly in what audiences get to hear: 1) performers who consider music, ANY music, as a mere vehicle for their ego and career, and 2) programming staff at orchestras and venues who are mainly of the manager type, for whom musical value or understanding can only be a minor issue since the work involved in creating a season is such a complex and sophisticated job, that the heart of the 'product' of the 'music business' is easily overlooked. And one could understand that easily: if you compare performance practice how it was in the 19th century and the beginning of the 20th century, with modern ways of organising a symphony orchestra or a chamber music series, the difference is hughe. At those times, great works (including very original ones) could still bubble-up to the surface and be integrated into the existing repertoire because of an underlying consensus about musical value. Nowadays, such process is no longer possible.
What to be done to this difficult situation for the development of serious Western concert music? I think best is to return to a traditional musical language, in the sense of picking-up that underlying dynamic of musical values that has produced so much great music in the past. This does not mean copying precisely an old language, but taking-up things that feel compatible with one's own authentic musical nature and forge one's own mixture of elements and use it as one's personal language, in all freedom. When new music uses important elements of languages which make-up the existing repertoire, there is a bridge of musical understanding in terms of language between composer and audience, and the composer can share his/her imaginings without the hurdles of inaccessibility. If done with enough sophistication, a new work can be both personal (= new) and immediately accessible (because relating to a more or less common language).
This touches upon subjects like originality, progress, the relationships between composer, performer and listener, modernist ideologies of the last century, the issues of living in the modern world, the meaning of history in the context of performance culture, and the like. They are treated in 'The Classical Revolution':
https://www.amazon.com/Classical-Revolution-Thoughts-Century-Expanded/dp/0486814483

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JohnBorstlap:
With music this has nothing to do, it is about sound patterns and if you like it, it is nice. But the notes are random and don't have any psychological dimension, as in music. It is a different art: sonic art. It is not supposed to isten to as music. Claims that this is a progressive form of the European musical tradition are false and nonsensical. It is a modernist fallacy, an ideological idea, an attempt to give it a respectability that it does not deserve because it wants something very different from music. It has to be enjoyed as Klangkunst, for the sheer pleasure of sound patterns, nothing more.