If you look at stackoverflow surveys you'll notice that those using Scala are amongst the happiest users of any language and are very willing to continue using it. It's growing slowly but steadily and Spark is also driving adoption. With some exceptions most criticism seems to be coming from those who haven't had much exposure to scala and trot out the same tired old material time and again. Once you grok scala it makes more sense. It's a bit like complaining that Mandarin is hard to understand if you are English. It takes time to learn but it's worth it if you stick it out.