This is what the theme means to me, and what it tells you about the Fraggle culture.
Fraggles, while most have important jobs, are carefree and appreciate the little things in life. Playing, dancing, singing, parties... etc. The philosophy of the song is pretty much the philosophy of the Rock. Dance your cares away. Don't worry, because whatever is to be worried about is a small matter (something that Boober and Wembly don't exactly follow).
The Doozers have a different, yet similar philosophy. Don't worry, focus on your job. A working Doozer is a content Doozer. And to keep things carefree and rolling smoothly, keep working.
As for Junior... well, he is the incompetant son of a king. His future is in tact, he has nothing to worry about, bumbling about like he does.
Though, I still think it's odd he sings the theme song if Gorgs hate Fraggles so much.