I'd maybe make the analogy that it's like the first ORM. Sure, you could write your own DB queries, but it just does what you want, and it's usually right.
Were ORMs the second coming? Meh. But it's arguable that they're still immensely powerful and useful and the way people write apps that interface with an RDBMS is permanently changed forevermore.
How did WordPress boost productivity? Fussing with hosting, CMS, plug-ins is a mess. I just went back to good old hand written HTML with pico.css. Got my site down from 8mb to 100kb
We don't think of rails as the second coming though.
same with code editors. of course a rails for all of code is cool. but iono, it's a code editor. i still use sublime.