In my personal experience, Scala in 2021 is de facto best language for business logic. Effects are easy, parallel code is beautiful and easy to reason about. Ecosystem is big and no other languages comes close to productivity I have with Scala.
For example, its very fast and easy to prototype code with ADTs and scale that code to big codebase. I rarely have to run my code and if I do - it most of the time works as intended because of the type system. Its like magic. In other languages if you want to write code without bugs you are stuck with TDD or a lot of tests. With Scala usually few tests are enough, everything else encoded in its expressive type system.
I would say the only big negative I see is using Scala as Haskell. With tagless final, Kleisli and so on. If you do - it becomes very hard to onboard new people and I am not sure the positives outweigh the negatives.
Tagless final is a good way to enforce the principle of least power, which has many advantages when onboarding inexperienced developers. It can become unwieldy if abused, but that's true for any style.
And if it really bothers you, then you can use your concrete "super monad" everywhere. It's the only way with ZIO, but you can also do that with other effects.
Regarding Kleisli, it's such a broad abstraction that you'll find examples everywhere, whether explicit or not. In practice, even with heavy usage of libraries like fs2 or http4s, it's mostly an internal implementation detail, in most cases you'll only see type aliases.
For example, its very fast and easy to prototype code with ADTs and scale that code to big codebase. I rarely have to run my code and if I do - it most of the time works as intended because of the type system. Its like magic. In other languages if you want to write code without bugs you are stuck with TDD or a lot of tests. With Scala usually few tests are enough, everything else encoded in its expressive type system.
I would say the only big negative I see is using Scala as Haskell. With tagless final, Kleisli and so on. If you do - it becomes very hard to onboard new people and I am not sure the positives outweigh the negatives.