1. Open source libraries are sometimes not maintained which is absolutely true but also just a general hazard of the open source software ecosystem. The solution in most cases is to just not use open source libraries that are somebody's hobby project (which the author very sensibly recommends). But that is true whether you are using Scala or not.
2. Spark is weird. Which is true but that seems like it is more to do with the idiosyncratic nature of Spark than it is anything to do with Scala. That is, Spark development is sort of its own category and poses certain problems that are pretty specific to Spark and you don't necessarily run into when you are building non-Spark project in Scala.