In the times of Mozart, Beethoven, Brahms etc. it was normal that the newest music is the most interesting music - the audience thought that as well as the players and of course the composers. Old music wasn't performed at all until Mendelssohn began to reanimate the music of Bach (this day shall be cursed). To hear the music of their times was so natural like listening nowadays to the newest pop songs.
What went wrong that 95 % of the classical music is the music of composers died a long time ago? It's the largest museum in the world, there is a lot of dust everywhere and all orchestras and conductors are oppupied to do the dusting. Who is guilty? The audience who likes to hear the well known music played by X or Y more or less faster, cleaner or whatever (but of course with faithfulness to the original, that is sacred!) or the program directors, conductors, players who like to fulfill wishes of the audience? Or the composers who refuse to write music which could be liked by many people? Which is so difficult to play and also to listen to it that all involved people abandon this music?
Anyway, I seldom go to a concert with non contemporary music and if this happens coincidental I miss the most important thing listening to music: the energy and spirit of a human living in the same times like me. Everything else is like visiting a cemetery. Or a just a museum.
