What is a good alternative?
It's got a strong, friendly ecosystem that encourages small, composable libraries. For every level of your application, there's competition - http servers, sql abstractions, front end libraries. And there's great resources to help you choose what works best for your use case - the Luminus docs, books, blogs, and several active forums for discussion with library owners and just regular developers.
Couple that with a community that really took Rich Hickey's "Simple made easy" talk to heart and the default immutability and functional paradigm and the abstractions that Clojure itself has to offer, not to mention the performance the JVM brings to the table, and I think it's a great language to hang your hat on in the long haul.
Also after programming for 4 years a bit I've felt the core of programming beyond CRUD/consuming APIs is about manipulating data structures. Having powerful utilities for this and not having to shove everything into classes and objects makes it really easy to get stuff done. Going back to Ruby feels like I'm working with a kludge in comparison. Everything that doesn't need to be a class is one, then you get caught up in naming things. Then you try to debug things to end up with an object that has 500 methods on it and you don't know where half of them came from because they were metaprogrammed in through 10 layers of indirection. Yesterday I tried upgrading to Rails 5 and gave up because I couldn't debug an outdated library in 6 hours without realizing I have to figure out what this library and ActiveSupport/Model is doing in order to make headway. Ain't nobody got time for that.