Did the people in the show seem happy to you? Did it seem like Bobby, Peggy, Hank, or Dale were satisfied human beings? Boomhauer is the only person that really seemed to accept their role in life without regrets, and that's only because I could never understand what he was saying.
Note: I didn't watch the show religiously.
We can agree that there were specific times when the characters were happy but I think we can also agree that there were times of deep sadness. Mostly the happiness was portrayed as being very superficial, and the sadness was generally existential and deep. In the episodes that I saw, this deep sadness was due to how the "traditional power structure" tried to mold them. It's a pity that they didn't break out of their molds, but as a show I think the zeitgeist was their deep dissatisfaction with their lives, punctuated with small insignificant victories.
Think about Beavis and Butthead. Do I think that it glamorized(to some extent) acting like a jackass? Yep. Did it make me want to act or be like either character? Nope. Do I think it "convinced" any normal humans into acting like jackasses any more than the evening news does? Nope.