I can only speak for myself and I'm more interested in getting a job done. If that means my UI component uses class syntax, and my state and communications channels are functional reducers, so be it.

I love JS because it's flexible and doesn't lock me into a paradigm. I can be as strict as I want to be. In the end, I think it depends on how someone thinks about problems. I tend to bend my thinking depending on the type of problem and how I might optimally solve said problem. When I need something else (often for performance), I'll circle around at that point for that part.