[zopa]

Agree with your thesis, but John Williams is the wrong guy for your point. He's a popular composer too, in his own way.

You could point to the Neo-Classicists -- although Prokofiev's dead, of course. Or there's Penderecki; perhaps a hard sell, but deserving.

[Darmani]

Definitely. But a major trend in art music relatively recently has been the mix of foreign and other forms with Western styles (and certainly true of the music I'm familiar with). I could hardly call Karl Jenkins or Tan Dun musical descendants of Beethoven. Perhaps I picked a name based on the wrong criteria.