I've got my problems with Rails: routing is overly complicated, the asset pipeline can be tricky, and so on. But Rails is very good at producing HTML and, in particular, partial chunks of HTML. As the current thick-clients-in-javascript trend cools off (it's happening, this was at the top of /r/webdev yesterday: https://www.reddit.com/r/webdev/comments/4iphv4/12_year_of_p... ) people are going to migrate back to HTML…
What makes you think that being able to produce HTML is such an important piece, and that Raila delivers better than most other frameworks?
http://intercoolerjs.org/2016/05/08/hatoeas-is-for-humans.ht...
and is the minimum level of complexity necessary for a human web interface.
Rails isn't necessarily better than other platforms at producing HTML: it does support rendering partials which is nice: http://guides.rubyonrails.org/layouts_and_rendering.html. So, rails is pretty good at it, but I can imagine other tools being perfectly competent at the problem as well.