Aside from the points already countered by others, note that the reddit post is 6 years old. Most likely, the poster had experience with Scala 2.10 or even earlier.
A lot of the points in their comments in that thread are in areas, that have changed a lot since then. For example, the collection library was completely reworked in 2.13, removing a lot of the uglier parts (e.g. that whole CanBuildFrom business). Type inference and exhaustiveness checking, which they criticize, has also improved.