+ Any decent developer can read decent code in Java or whatever normal language and get along just fine.
+ Only a few people can deal with Scala - and even fewer if there's a log of specific project Scala weirdness used in a particular program.
So sure - among a narrower set of 'Scala friendly' developers, and possibly within that even narrower set of people familiar with the 'Scala weirdness' of a particular project - those people can 'get along fine'.
The problem is that this can be a pretty narrow set of people.
Scala would have to represent a pretty big advantage to propose it's general weirdness as something to bother with.
I don't think it does - hence the 'de-adoption' of various entities.
My gut tells me it's past the threshold - the 'extra power' offered Scala just isn't quite worth it's weirdness for most things, and so most devs won't learn it ... and so then it becomes less valuable from a business perspective.
It's possible we may have it peak Scala.
We'll see I guess.