What traits do you consider run-of-the-mill avant garde in classical music today?

Octatonic scales, quartal and quintal harmonies, constant changes of meter that make the music sound somewhat unmetered, [pass on structure], an orchestration assigning lots of melodies to the percussion.

Also, it is important for your music to have some kind of extramusical meaning, though not like those you find in the 19th century. Think of a relative dying of some little known disease, or your heritage from another country, preferably an Asian country. In fact, these personal facets may be much more important in winning composition contests than technical skill.

This questions sounds like composers have academic discussions at the water cooler. This is really more of a social issue than anything technical about the music. And one not really worth worrying about for a composer.

When Schoenberg invented serialism around the turn of the 20th century is was a revolutionary idea. Now most conservatory students will write a model 12-tone composition in their second year of music theory. The orchestration of Schoenberg, Webern, and Stravinsky is now the manual for writing film scores. The so called "new complexity" is undergoing a similar fate. Anything that endures long enough is in danger of becoming mundane.

Everything is derivative of something else to a degree. That only becomes a bad quality when it gets in the way of a piece because as you say it "contains nothing really original"