Imo functional programming is one of those things that makes sense from a theoretical perspective, but comes with compromises when it comes to reality.
The thing about functional programming is that the confidence you get from immutability comes at the cost of increased memory usage thanks to data duplication. It's probably going to create a ceiling in terms of the absolute performance which can be reached.
There are just other ways to solve the problems like NPE's and memory safety, like ADT's and ownership rules, which don't come at the same costs as FP.
The thing about functional programming is that the confidence you get from immutability comes at the cost of increased memory usage thanks to data duplication. It's probably going to create a ceiling in terms of the absolute performance which can be reached.
There are just other ways to solve the problems like NPE's and memory safety, like ADT's and ownership rules, which don't come at the same costs as FP.