Ausgedient literally means "served its purpose" or "is obsolete." It's a strong and somewhat formal word that you don't often hear in popular music, making it quite unique and memorable.
In the song, Xavier Naidoo uses it repeatedly and emphatically to declare that various political entities and systems (like the CDU, SPD, USA, and even specific politicians) have become irrelevant and are no longer fit for purpose. It conveys a powerful message of disillusionment and a call for change, making it a central theme of the song.
Xavier Naidoo's "Verschieden" [Different] is a really direct song about feeling fundamentally at odds with someone, or even society itself. He sings, "Wir sind so grundlegend verschieden" [We are so fundamentally different], highlighting a deep divide. While the other person wants to "immer höher hinaus" [always go higher], he just wants to "wieder hier raus" [get back out of here]. It's a classic clash between ambition and a desire for something simpler, or perhaps an escape from the current system.
He feels like he's "wieder geboren" [reborn] while the other person thinks his "Geist sei verwirrt und ich schon wieder verloren" [mind is confused and I'm already lost again]. This isn't just a personal disagreement; Naidoo broadens it to a critique of political and economic systems. He boldly declares that "Zins und Zinseszins haben ausgedient" [Interest and compound interest have had their day] and even calls out political parties and leaders like "Die CDU hat ausgedient" [The CDU has had its day] and "Barack Obama hat ausgedient" [Barack Obama has had his day]. He's basically saying, "Why aren't you part of the solution instead of always being part of the problem?" It's a powerful and blunt call for change, rooted in his feeling of being completely different from the prevailing mindset.