Scala has a really steep learning curve when you encounter user libraries. Though I am moderately experienced in functional programming, I still have difficulties understanding scala libraries from very experienced users. It almost feels as if I didn't understand the language at all.

It is true that you can use the JVM ecosystem, but you'll see that your code doesn't look like scala at all. Then you look for scala ported version of java libraries (some essential but boring libraries like xls read/write) that isn't likely to be maintained actively