There's a blooming ecosystem of pure functional programming libraries. Or even two ecosystems: Typelevel and ZIO.
My company uses Scala a lot with with these ecosystems (my team is on Typelevel, another one is on ZIO) and in fact Spark and Akka is what we're trying to avoid as much as possible. Once I got used to the composable nature of FP and static types - both Spark and Akka just feel clumsy and unintuitive, like maintainers of Spark chose Scala because it was a "Java with fancy syntax" back then, ignored most of benefits of static types, HKT, immutability, type classes etc. If there's future behind Scala - it definitely doesn't lie in Apache land. Akka is slightly different and probably has higher potential, but just an overkill for most of use cases it's advertised for.
My company uses Scala a lot with with these ecosystems (my team is on Typelevel, another one is on ZIO) and in fact Spark and Akka is what we're trying to avoid as much as possible. Once I got used to the composable nature of FP and static types - both Spark and Akka just feel clumsy and unintuitive, like maintainers of Spark chose Scala because it was a "Java with fancy syntax" back then, ignored most of benefits of static types, HKT, immutability, type classes etc. If there's future behind Scala - it definitely doesn't lie in Apache land. Akka is slightly different and probably has higher potential, but just an overkill for most of use cases it's advertised for.