I switched from Rails to the node.js ecosystem back in the 3.2 to 4 transition, however looking back I share a similar sentiment as the OP.
I recently initiated the backmigration and my approach thus far however has been to take out the "administrative" part out into Rails to benefit from all the useful conventions there, but keep the "business services" in JS or Python and have the two communicate. Best of both worlds, and the potential of all of rubygems, npm and pypi combined.
This is a good approach I think. Rails is outstanding at delivering a good CRUD experience and data model management - sir I find it powerful to build the data model and admin tools using it, and allow other frameworks to access either the database or specific services as needed. Best of all worlds!
Reminds me of what I did to bring AI into my SpringBoot Java app. I just created a Python-based WebService (microservice), that deploys as part of my docker stack, and now I get the benefit of everything going on in the AI world which is mostly Python, with no lag. Meanwhile other Java Develpers are busy trying to port all that stuff over into Java language. To me that porting is just a waste of time. Let AI stay in Python. It's a win/win, imo. Of course I had to learn Python, but as a Java Dev it came easy. Other Java devs are [mostly] too stubborn to try Python if you ask me. Sorry if this drifted off topic, but it shows how you don't have to be a purist, but you can just do what works and is easiest.