It got preachy. Now it seems to spend most of its time trying to convince the kind of people who'd never watch it that everyone should be judged by the content of their character, not their color/gender orientation/medical condition/weight/home life etc. etc. etc.
The problem is that the kind of people who do watch Glee already agree. So they're preaching to the choir, with anti-stereotypes that have become as stereotypical as the stereotypes they're combatting. The Crippled Guy; The Sensitive Gay Guy; The Girl With Downs Syndrome; The Fat Girl; The Asian Couple; the Black Guy and so forth.
They don't come across as individuals, but rather as representatives of some category of humanity that the writers think have gotten a raw deal.
It's like the 13th Century Everyman plays, with each character named for a trait--Everyman, Lust, Anger, etc. Hiss the villain, cheer the hero. Bo-ring.
Not to mention how much the show's music represents the tastes of 40-something male homosexuals rather than contemporary high school students. Retro much?
Ellen DeGeneres first came out when she had a sitcom, which she proceeded to destroy by using every episode as a soapbox. But she learned her lesson, and her daytime show is hugely popular. She doesn't hide who she is in the slightest; she just doesn't make it the show's prime focus. The Glee team should go to Ellen for advice.
Glee should focus on the music actual high school students today actually like. Its casting should be based on interesting people rather than didactic propaganda objectives.
Maybe they could get Joss Whedon to give them a plot arc for the next season...he was able to take a hackneyed genre--the superhero action movie--and turn it into something actually interesting (i.e. The Avengers). Together, Ellen and Joss could really turn this show around.
Oh, and drop the NY suplot. Either spin it off or forget it. Personally I'm sooo over Lea Michelle's character. Glee isn't Smash. And now Smash simply isn't. Might be a hint.
Lastly, one thing that could really shake things up would be to do a ballad week and bring in (for just one or two episodes) 13 year old singer Jackie Evancho, who has a voice so beautiful--regardless of age--that many grown people weep when she sings.