[nv-vn]

>In mission critical portions of systems people will use a functional style and try to isolate state, while most things in an OO style will be just fine.

What makes you think that programmers who are used to writing in FP style for mission critical components would step away from FP for OOP for less important code? In my experience, most of the time functional code is often more succinct and easier to write. I don't think it would benefit anyone to write the majority of an application in the more verbose style.

>languages like Go explicitly making trade offs towards simplicity

I think Go is a counterargument to your point here. It's simplicity makes it much less suited for multi-paradigm programming than a complex language like C++ or Scala.