IMO, it really depends on the team you join, as with most programming projects. Scala can be used in a classic mutable OOP manner, as if you were writing Java in 2005, or if you heavily buy into pure FB libraries it can be used basically like it's Haskell, but IMO neither of these approaches embrace the strengths of the language. It's meant to be a true mix of OOP and functional paradigms, not going extreme one way or the other. The object oriented aspects let you embrace great OOP software architecture patterns like Domain Driven Design, so that you can really model the business domain clearly and faithfully. Then the functional aspects allow you to implement a "functional core, imperative shell" style, that's really easy to reason about, and easy to make concurrent (safely), while also having excellent/safe/descriptive types like Future/Option/Try and ADTs.
It sounds like you've worked with a group of people who want to treat Scala like it's Haskell, but that's a minority community that IMO isn't really embracing the strengths of the language. I've worked on projects that go all-in on libs like Cats and Scalaz, and I agree that they're mostly unnecessary complexity that also obscure the modelling of the business domain. You're going to massively confuse newcomers with all the Applicative/Effect/Monad/Monoid/Functor/etc. talk, for next to no benefit. Actors are a bit of a different story - excellent for the 1% of times where you really need them (lots of mutable state and lots of concurrency), but 99% of the time you don't need them. Some devs are enamoured with the mathematical purity of pure functional programming, without properly considering how hard it is to understand for most other devs. If you let these types take over your company, that’s a cultural problem, not really a language problem.
> ... programmers are increasingly facing new challenges for high-level domain modeling, rapid development, and, more recently, parallelism and concurrency. It seemed to me that a unification of the traditional object-oriented model with functional programming concepts was feasible and highly desirable to address those challenges.
I completely agree, and have yet to find a better language than Scala for the above demands, assuming you really embrace the OOP/functional mix. I've been writing lots of Scala at my day job for the past ~5 years, and it's my favourite language. I've worked on backends in Scala, Java, Go, Python, PHP and Node, and prefer Scala to all of them.
I also agree with Li Haoyi - it's becoming a really solid, stable, reliable language, with improvements focused on the build tools, compiler, and the odd language wart, without significant changes to syntax/style, which is great. It does take awhile to learn, and you do have to be careful about what style you program in, but I think if you just embrace the language's OOP/functional fix, and for "core style" mostly stick with the standard library (Future/Try/Option/etc.) vs. going crazy with Cats/Scalaz/Akka/etc. (unless you REALLY need Akka specifically), it's an outstanding language.
It sounds like you've worked with a group of people who want to treat Scala like it's Haskell, but that's a minority community that IMO isn't really embracing the strengths of the language. I've worked on projects that go all-in on libs like Cats and Scalaz, and I agree that they're mostly unnecessary complexity that also obscure the modelling of the business domain. You're going to massively confuse newcomers with all the Applicative/Effect/Monad/Monoid/Functor/etc. talk, for next to no benefit. Actors are a bit of a different story - excellent for the 1% of times where you really need them (lots of mutable state and lots of concurrency), but 99% of the time you don't need them. Some devs are enamoured with the mathematical purity of pure functional programming, without properly considering how hard it is to understand for most other devs. If you let these types take over your company, that’s a cultural problem, not really a language problem.
Odersky describes why he created the language here: https://www.signifytechnology.com/blog/2018/01/why-scala
> ... programmers are increasingly facing new challenges for high-level domain modeling, rapid development, and, more recently, parallelism and concurrency. It seemed to me that a unification of the traditional object-oriented model with functional programming concepts was feasible and highly desirable to address those challenges.
I completely agree, and have yet to find a better language than Scala for the above demands, assuming you really embrace the OOP/functional mix. I've been writing lots of Scala at my day job for the past ~5 years, and it's my favourite language. I've worked on backends in Scala, Java, Go, Python, PHP and Node, and prefer Scala to all of them.
I also agree with Li Haoyi - it's becoming a really solid, stable, reliable language, with improvements focused on the build tools, compiler, and the odd language wart, without significant changes to syntax/style, which is great. It does take awhile to learn, and you do have to be careful about what style you program in, but I think if you just embrace the language's OOP/functional fix, and for "core style" mostly stick with the standard library (Future/Try/Option/etc.) vs. going crazy with Cats/Scalaz/Akka/etc. (unless you REALLY need Akka specifically), it's an outstanding language.