[EDIT: I see that SeptimalTriTone posted a somewhat similar line of thought above just as I was posting mine].
These "tonality" discussions are always a little bewildering for me. I don't want composers to write in the style of the 18th-century or 19th-century any more than I want to wear 18th-century clothes or live in a 19th-century house. I love the music of the 18th and 19th centuries just as I love the poetry and fiction of the 18th and 19th centuries. Yes, there are certain features of 18th and 19th century poetry and fiction that transcend the limits of their era. But they are also knee-deep in their milieu, not only in terms of setting, but style, language, worldview, etc. And so too is the music. In some ways, it transcends; in some ways, it's stuck in another time. I have lived a good chunk of my life in the 20th century and am now in the thick of the 21st. I want artists to speak to me in my native tongue -- to speak to me in contemporary musical parlance. My world is full of sounds that didn't exist in the 18th and 19th century, and I presume that artists hear those same sounds and those sounds are part of their palette.
For those who are uncomfortable with contemporary musics, my first question is: What specific examples are you thinking of that make you uncomfortable that you yearn for "tonality"? Are you aware of the wide ranging works and composing styles that may be less discomfitting? (Arpeggio posted an excellent set of links above to threads where a good and wide-ranging set of examples are cited and discussed). Other questions follow: Why do you yearn for music of another era? If artists actually composed faux-Haydn string quartets, would that satisfy you? If artists composed faux-Beethoven symphonies or faux-Wagner operas, would that satisfy you? What are you asking for from your artists?
In fact, contemporary artists, on occasion, deliberately compose in or draw upon earlier styles. Two examples. The first is a rather avant-garde-ish composer, Charles Wuorinen, who playfully took some Renaissance dance music pieces and cleverly re-orchestrated them for contemporary performance. Here's the YouTube:
One could call those "Etudes" in the sense that they are studies in instrumental coloring, that Wuorinen cleverly took advantage of the fact that Renaissance composers might have allowed a variety of instruments to play a certain line (giving him the opening to use 20th-century instruments like a clarinet) and that Renaissance performers might well have improvised using a variety of techniques to punctuate the melody (giving him the opening to use 20th-century techniques like glissandi and flutter-tonguing). What are we to do with such deliberate archaicisms? Is that what we want fulltime? And what about the artist's intentionality? Are not such works more examples of humor and playfulness?
Another more serious example: Dobrenka Tabakova is a young contemporary Romanian-born British composer who has composed a work called "Suite in the Old Style". She deliberately plays on certain late Renaissance / early Baroque styles in this piece, but she is also consciously writing a serious contemporary work. But then, this is just one work in her repertoire. I doubt she wants this to define her oeuvre. This is simply her loving nod to music of the past. But I suspect that she thinks of this as expressive only a tiny part of her soul. She has other things to say.
Let me use literary examples: If I write a novel in the style of Dostoyevsky -- and I mean, really in his style, using his mannerisms, his sentence structures, his character developments, his plot twists -- what would I be doing artistically? Mocking him? Being ironic? Of course, one can still write a good 20th-century novel and be epic. Witness Gabriel Garcia Marquez'
One Hundred Years of Solitude. But Marquez told the story as he did, in a rather dizzying late 20th-century way, with its folkloric "magical realism." And he told the story of anguish and joy of a family in a century of violent Latin American politics. I am happy he wrote a 20th-century novel and not a faux-19th century one. He carved out a voice that fit his story and our world. Its "magical realism" might discomfit those who want a 19th-century novel of manners. And it may be hard the first time through to figure "what really happened". But Marquez was speaking powerfully enough, uniquely enough, that he was awarded the Nobel Prize for literature and became one of the towering figures of 20th-century literature. Should I have insisted that he write like Jane Austen or Cervantes?
I think of T.S. Eliot's classic essay "Tradition and the Individual Talent." How much of the "tradition" must our "individual talents" embrace for us to listen to them and be grateful for what they say? I don't think this is about "tonality". I think it's about how much we are willing to let our artists speak to us in beautiful -- and beautifully discomforting -- ways.