Why was the one-week season of the Boston Ballet, celebrating its 50th anniversary, such a painful disappointment? This company is talked about as though it were on a par with our other second-tier companies, just behind ABT and City Ballet: San Francisco, Pacific Northwest, Miami, and by a generous stretch of the imagination, Houston, and we haven’t see it in New York within living memory. The disappointment comes from the unwelcome revelation that although its dancers are devoted and agreeable, it’s a gigantic artistic mess. The pain comes because the company is clearly so proud of its awful aesthetic. They’re up there in Beantown isolated from the realities: Sorry, guys, but William Forsythe is old hat (and was a pernicious phenomenon when he was new hat); Jorma Elo—the Finnish resident choreographer—churns out frantic and empty pieces every 10 minutes; and most of the rest of the repertory on display here is what we used to call Eurotrash—although Europe’s in enough trouble already without have to shoulder the blame for a tsunami of bad art.