> Why is the gap between these two perspectives so large? My conclusion is that there are major, well-justified reasons for why people strongly dislike functional languages.

Now that (nearly) every mainstream language has lambda expressions, there are very few patterns in functional programming that cannot be replicated in mainstream languages, which means that moving to a pure functional language now provides strictly fewer choices when problem solving. In order for a programmer to accept a language with strictly less expressive power, those new restrictions must solve problems that the programmer actually cares about.

Rust reached adoption because mainstream systems programmers recognized that memory errors are a huge problem and dealing with the borrow checker is worth it to solve them. Static typing reached mainstream adoption because it made coordinating work in a large team dramatically easier and solved refactoring.

Functional-style programming has hit the mainstream—embedded within imperative and OO code—but purely functional languages have yet to make a good case for their additional restrictions, and I'm not convinced that multiprocessing is that case. Golang mainstreamed a very effective model for multiprocessing in an imperative environment that solves most of the problems without asking programmers to completely change the way they write code, and that model is increasingly being adopted in other languages (Java's project loom, for example).