When you work on any medium-to-large Rails project, and you want to run a quick unit test to test some new functionality for your new class that inherits from, say, something in ActiveSupport, and AS pulls in a bunch of gem code that is opaque to you, and your class names a module that wasn&#x27;t loaded yet and so it gets dynamically loaded (warning: global mutable state has been altered, causing weird load-order bugs), and then THAT module triggers other loads of things <i>it</i> depends on, and one of those monkeypatches a bug in an old version of some gem which has actually since been fixed but is still being monkeypatched with old code and causes a corner-case bug that you haven&#x27;t discovered yet (shameless self-plug: I actually wrote a gem to help manage that stuff: <a href="https:&#x2F;&#x2F;github.com&#x2F;pmarreck&#x2F;pachinko" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;pmarreck&#x2F;pachinko</a>), and your unit test ends up taking, like, 30 seconds to just <i>load your stack of dependencies</i>... (I&#x27;ve actually seen 40 sec stack loads, in the wild, at past jobs)<p>... Ruby is still slow.<p>Sure, there are band-aids to assist with that stuff (Guard, Zeus, etc.), but you&#x27;re still dealing with spaghetti-dependency, mutating-global-state, side-effecting hell.<p>Which is <i>exactly</i> why I now want to work with Elixir and Phoenix instead.<p>Note: It IS possible to write Ruby in such a way that almost none of this stuff actually comes to pass. But even if you do, you&#x27;ll have to deal with an entire library of code that does <i>not</i>.