What are the criteria by which the work of today's composers should be assessed?

[ahinton]

It's quite a different matter for a performer or peformers to address an audience (be they singers, players, actors or whatever) because they do this directly -

Hmmm, but an opera staging - or any other kind of theatre production - is a creative work in its own right, albeit relating (in most cases) to a pre-existing piece of work. It goes rather further than merely interpreting or performing :)  Rather too much farther, some would say ;)

Indeed so!