Adding FP features to an otherwise-mutable language has always seemed a mixed bag to me. Obviously it’s nice to have those features, but you don’t get the immutability constraint that makes development so much more predictable.
FP is great at the high-level for orchestrating workflows and in the lower-level processing/transforming/aggregating over streams of immutable records. OOP is great at the high-level for independent communicating services/life-cycles and fine-tuned memory bound algorithms and needing state machines lower down.
You generally know what parts of your code mutate and what don't well enough to get the nice side-effect free usage from your functional parts.
Someone smarter than me once said: OOP? FP? It's really all just about being principled about state. A closure is just an object with one function.
I’m not saying it’s bad to add FP bits to other languages. I just haven’t seen the same benefits as when I know what a called library/module can and can’t do with my data.