Scala support in IntelliJ is ok, but still not great. There are some Akka constructs IntelliJ underlines in red for years and JetBrains doesn't fix it. I've never seen something like that with Kotlin.
The hard truth is that Scala was not designed with tool support in mind and it probably never will be. For example hierarchical implicit conversions, while powerful, are terrible for tooling.
> Scala was not designed with tool support in mind and it probably never will be
You should pay attention to what's going on in the ecosystem. Dotty comes with LSP support. The Scala Center's main focus is tooling. JetBrains has been pretty committed and cooperating as of late. And several projects are building serious alternatives to SBT.
Intellij still can't figure out how to handle implicits. At this point i have an intuition about the errors that idea reports as errors but actually aren't'.
The hard truth is that Scala was not designed with tool support in mind and it probably never will be. For example hierarchical implicit conversions, while powerful, are terrible for tooling.