Hack Reactor focuses entirely on JavaScript and Web Development, after baking in the basics (algorithms, logical thinking, recursion vs iteration, introductory functional programming and TDD). And it is incredibly successful.
I think you're underestimating the difference between college and immersive learning. College is about many things, your major and focus being one of them. Immersive learning is about one thing. In Hack Reactor's case, it's becoming a competent Web Developer.
Elon Musk's response in this thread (https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk...) rings true. Almost no college is teaching Web Development, and so the students get little class based exposure to it, and stumble through many pitfalls. An immersive experience gives you the trunk and several branches, and then frees you up to go deep into whatever you care about.
And smart, voracious people who are eager to learn and better themselves quickly outclass everyone else.
Oh, and I could code competently before I went to Hack Reactor (I was a contractor). I went to gain deep web experience, work in crossfunctional teams, and have a safe place to fortify the foundational soft skills which are absolutely essential for productive software developers.
Oh, and the ROI is insane.