I'm the opposite. This release excites me more than it did for Rails 4.
Turbolinks 3 sounds like it's going to be real nice. My biggest reason for using SPA's are not the components, or the data flow, or the states, etc. It's for the partial rendering and the nested views. With Turbolinks 3 coming out, if it is as advertised, then I will pretty much be reaching for Rails for most of my projects.
I've moved on from Rails to Node for websockets. For ActionCables, the real-time library for Rails, I have to admit that it does kind of sound like a PITA to have a second server running for it. Doesn't sound right. But I can't judge it before it comes out (nor do I really have any right to judge. It's so easy to be entitled as a FOSS user). But if it is a pleasure to use, just like the rest of the Action* family, then that's another nail in the coffin for my use case for anything else. But then again, my needs and your needs may be different. I usually build small to medium sized apps that will never hit 4 figures in terms of users.
It sounds like you're looking for that "magic" you've felt when you first got into Ruby and RoR. We all do! But things like Rails once comes once in a blue moon, so even though it may not be the new hotness, I just like to appreciate that it happened. I don't think you'll find any other tech that will give you that "this is it!" feeling like Rails did for a long while.
In the mean time, instead of stressing out about tools, just focus on writing good software.
What do you mean JS is still a second class citizen? I'm unfamiliar with Rails asset pipeline.
Do you just mean that the asset pipeline doesn't really have as much features as other build tools like Grunt and Gulp? Or is there something about asset pipeline that prevents you from using JavaScript to its full potential? (Genuinely curious. Not familiar with the JS side of Rails)