I did not mean to suggest it was a bad thing...or a good thing. I was sensing from the OP's post that s/he was presenting a comparison between two different value systems both set in stone. And while religious worldview and values can be conceptualized as "set in stone" for the sake of argument (though they do change over time), psychology and psychotherapy should not be conceptualized as such. So "effective practice of psychology" changes all the time and is in fact different between different schools despite most of them adhering to APA ethical code, at least from a legal standpoint. And as much as some psychologists like to think of psychology as a science like physics, it's not. Not even close. Like you say, it is affected by social change. This is not necessarily a bad thing...or good thing...but the influence of social, cultural, and political forces and groups in how we define illness/health and therapy means that our field is different from a purely scientific field like physics.
As far as homosexuality never going back to be seen as pathological, I would like to disagree with that. This is not a blanket statement. But as we learn more and more about brain and mental health, it is possible that some types of homosexuality will be seen as pathological. In particular if some types of homosexuality can be divorced from "identity." Once it's made into a behavior, it's easily pathologized. It will never been seen as a sin because that's the religious view, not psychological view. But pathological, it's possible. Let me clarify that I'm not singling out homosexuality. Pretty much any kind of behavior you can think of can be seen as pathological, as dysfunctional, as harmful. Think of a hetero person "obsessed" with anal sex. Anything that can cause distress and/or dysfunction in some situation can be pathologized. That's why I love comparing DSMs. I recommend everybody do this when they feel depressed. They'll get a real chuckle out of it.
I wish psychology WAS moving in a reliable direction like you say. But I doubt it. Psychology is moving in an exploratory way, like when you're learning a new subject. It explores something, jumps around, goes back to it, a paradigm shift....It's a young science, less than 150 years old, we're just getting started.