I love the character of Comic Book Guy in The Simpsons because it's the show's creators, even though they appreciate their fans, standing up to the overly obsessive Comic Book Guys with the integrity and courage of the barman who refuses to serve you drinks when you had way too much and saying:
"Look, I like that you appreciate our work, but tv is supposed to be the epic icing on the cake that is your life. It is NOT supposed to be your life, not supposed to be your childhood, not supposed to be your identity, not supposed to be your obsession. Treating it like that does to art what stalking does to romance and what religious fundamentalism does to spirituality.

Eminem makes a similar point in "Stan": don't make me the center of your life. You have a life of your own.

Coming back to the title...and to aother classic animation series: South Park and last season's Member Berries.
You can be forgiven if at face value you don't understand what's bleak about the warm, fuzzy feeling of nostalgia but until this generation, who was nostalgic?

Old people...DEPRESSED old people. Those who seem so afraid of the present and future you'd almost with death came to free the poor things and bring them back to a World of 8-tracks and Reagan speeches.

Among nerds, you have people in their twenties and thirties speaking like the best of their lives stopped at age 13 and the rest is just waiting to die and 'membering their old tv shows. Understand what's bleak about it?
At 30, you're not supposed to be nostalgic. You're supposed to be making and living the awesome stuff you'll be nostalgic about later in life...and certainly not live your live for someone else's creation.