I find that functional languages are an admiration of it's own idealized self. Their pursuit of mathematical (lambda calculus) purity forgets that systems run in the real world and not in theory. Yes, for academia and advancing compilers, they are great where idealized theory is the endeavour. However, their idealism is neglectful of the limitations and realities of computing for commercial development. Why be shamed for wanting to allow side effects and mutating objects? Especially when functional programming just further restricts object orientation.
Limitations
To illustrate my point of limitations within computers, let's use the typical functional programming example of calculating a particular value for the Fibonacci sequence.