Re: implicits - just try doing anything in cats. The whole thing is hugely based on implicits, which you need to import with magical import invocations (which of course the compiler has no way of suggesting to you).
Cats imports bring in "implicit classes", which are a way to extend existing types with new methods, in a way that works even with parametric types in a type-safe way. That's the way to get ad-hoc polymorphism (aka typeclasses) in Scala.
`import cats.implicits._`
Done.
And once you start understanding the typeclass hierarchy a little bit, finding the specific syntax and instances comes pretty naturally.
Of course it does. And since Scala 3, it does suggest to you the imports you need for implicits. And IntelliJ does recommend imports even for Scala 2.
Regarding cats, the codebase has been restructured, so that you won't need the implicit imports (or not as much at least): https://meta.plasm.us/posts/2019/09/30/implicit-scope-and-ca... The trick there is that the Type class instances were moved to appropriate companion objects which are searched by the compiler by default and thus the used doesn't need to do any manual imports.