I know that it's 2008 calling, but seriously: when did Heroku, Github and the bundler/gem ecosystem stop qualifying as accessible? Deploying an MVP Rails app with sophisticated functionality is so effective that it still qualifies as erotic.
For me, the most compelling example of progress coming from the JS camp was my shallow investigation of the Expo platform for React Native. It has some genuinely sexy developer ergonomics features which I'd love to see make their way back into Rails.