I watch Glee and I recently turned 39. The show most certainly isn't what it used to be, and it keeps making changes that I feel move it farther away from what it used to be in bad ways, but every once in awhile it still had flashes of its original spark. The most recent round of changes may have pushed it past the point of no return, but I think it's too soon to tell.
I think Glee's biggest weakness may have been that even when it established secondary characters of interest they frequently came and went w/out explanation, which doesn't make a ton of sense if the characters are high school students. Yes, the show was willing to lampshade this in ways that were occasionally entertaining, but it strikes me as a bad idea to effectively lampshade your own writing weaknesses. It would be like Captain Picard actually saying, "Well, that's a problem they'll have to solve for themselves, because we're off to a different adventure!"