Rails (or ruby on rails) used to the most popular web development framework just a couple of years ago, but it's not so popular now. If you are struggling to make a decision, this post may end up saving a lot of your time. But it is recommended that do research of your own about the technology and what it does best, will it be a good fit for you?
There is never a simple answer to questions like these. And it depends on what you want to achieve by learning this technology. Do you want to build your project, get a job or just get started with back-end development?
My Opinion
If you're still confused after reading this post
My opinion is just start experimenting even if end up preferring some other technology you'll still take away a lot from learning it.
I am looking for a job
But first, if you are new to rails and trying to decide whether or not to learn rails let me make this easy for you. If you are hoping to land a job by learning this, you probably won't find one. Rails is still used by many big companies like Github, Netflix, Twitter, etc. it is really difficult to find job vacancies and get it. You are better off with something that is more commonly used, like Django is an amazing alternative or you can never go wrong with javascript or any of JS-based frameworks.
I want to build a project of my own
If you are looking for a framework to build a side project, and maybe have a full-time job or are a student or just simply don't have a lot of time to work on the project. Then you should learn Rails, it'll be worth the effort, it will make your life way easier. Go through documentation especially if you have prior experience of working with other back-end languages or if you learn better by reading or watching definitely checkout Michael Hartl's 'Learn enough to be dangerous' series, you should quickly get comfortable with MVC model of rails.
Learning as a student
If you are a student and new to back-end development, it is a good idea to learn rails just to learn more about MVC and to get some real experience building web apps. Rails makes it very easy to make a basic web app, you can also do a lot of cool stuff quickly and effortlessly like user authentication, admin section etc. Learning rails can also help you build any project of your own. But if you are pretty good in some other backend technology you could use the time in getting better at it, as I said earlier there aren't many jobs requiring rails.
Hope this blog post will help you save some time giving you more time to work on your project or learning other stuff. Talk to people you know who know rails about their thoughts. If I missed anything please let me know through comments.