I feel the same way as the OP, but it's a bit difficult for me to avoid.
Still, I've backed off from partisanship greatly, and I would be wary of any who advise you to remain involved in that. Doing so has been beneficial both to me, my faith, and I find I'm a bit more persuasive to those capable of being swayed.
As Schultz wanted to define "involvement," so too should we define the "responsibility" to be involved. I am not against using politics to pursue what we are charged with doing, but I also don't readily detect a "responsibility" to be involved in politics from scripture or tradition.
Similarly, when is it our responsibility to become involved? It seems that people would disagree on that. Governmental wealth redistribution and anti-abortion activism? I would wager that while some would be for one, they would likely be against the other, but both thinking their positions are the truly Christian one (That debate is a different topic).
Regarding your post, Dave, I don't see your move away as a bad thing at all. I think many of us have been similarly moved. Perhaps some are still called to be involved while others are better off distancing themselves.