I agree with the sibling comment that this is an unfair summary of Rails' evolution and impact. I gave a talk about this when Rails turned 10: http://www.recursion.org/looking-backward/

It's hard to overstate how incredible Rails was compared to the what most people were writing in 2004. In both the frameworks that copied it, and those that reacted to it (like Sinatra) it has been widely influential.

As to the particular point, yes, there has been a lot of framework churn; but it also does far more than Sinatra. But there's more than one Rails app that's been upgraded all the way from 0.5 or whatever all the way to 5.0.