Is there a reason for the greater good that I ought to consider voting for him that I've missed in my aggravation?
Not for the greater good at all, but the major driving forces keeping him there (my understanding):

1) he's stuffing the judiciary with right leaning picks. Meaning well after he's gone, he'll be indirectly responsible for conservative policy. 2) for some its all about abortion, and anything that can stymie abortion or outright make it illegal is a good thing. 3) the rest of the agenda is specific groups wanting less regulations (eg dumping waste into our waterways for coal producers).

Plus Russia. Moscow Mitch isn't going to do anything to secure elections or sanction Russians, because he got a Russian oligarch to invest 200 million into an aluminum mill in Kentucky.