Time for another Crackpot Allyn Theory!
As we know, in the final Deep Space Nine episode Worf is appointed as the Federation’s Ambassador to the Klingon Empire. When we next see Worf, in Star Trek: Nemesis he is apparently no longer an Ambassador as he attends the Riker/Troi wedding in a Starfleet uniform and is then shown serving aboard the Enterprise-E and taking orders from Picard and Riker. What gives?
Start from the premise that being an Ambassador is not a permanent career move. An Ambassador serves at the pleasure of the government that assigns him and as long as the government to which he was sent is willing to accept him.
Worf would be acceptable to the Klingons for as long as Martok remains in power. The Left Hand of Destiny makes it clear that there are Klingons who resent Worf and will always resent Worf. There are rival houses that would like nothing more than to use Worf as a battering ram on Martok’s house. If Martok’s government fell, the succeeding government might not be as disposed toward Worf. Imagine if Drex took control of the Empire. Drex would, in a heartbeat, order Worf’s expulsion from Qo’noS.
That explanation really doesn’t put Worf in a bad light. His diplomatic mission doesn’t fail for anything that he did as an Ambassador. Instead, it’s his history that becomes an impediment to his work.
At the same time, what’s to say that Worf, abrasive as he is, wouldn’t make enemies in the Federation Council? They could have him recalled.
Worf as the Federation Ambassador to Qo’noS makes sense, given who Worf is and his unique perspective on the Federation and the Empire. But a Worf assigned as Ambassador to Vulcan or Andor or Cardassia doesn’t make any sense for Worf.