So-called liberal churches and synagogues are mostly dying because their “product” is self-destroying. These churches almost always don’t preach much moral law — or even preach against it. They think this appeals to people. Well, yes, epicurianism including “if it feels good, do it” -— has always had an appeal. But people who decide to live that way quickly determine they really don’t need much validation - and particularly not from a God they mostly don’t believe in (or who they think doesn’t have anything to say about their lives) anyway. In short, the lib churches are dying because they offer nothing anybody wants beyond perhaps for a transient moment in their lives.
No wonder these "churches" are dying.
If you're just fine with sin, you might as well watch football, or sleep in.