Ex: C doesn't have methods, but if you store most of your data in structs then you can easily do two things:
1) find all the places where the header defining that struct is included
2) Do a global search for the struct name
Both will present you with a nice list of places that data is used, and show the functions that accept it as an argument.
Where as with Ruby - I basically have to use RubyMine to get anything even sort of working, and even then it chugs along very slowly trying to do it. Solargraph in VSCode doesn't really work at all (at least 50% of the time it finds no definition for me) and just using a basic editor is a nightmare. Sometimes you can do a global find for "def [classname]" but that only gives you the definition, not any of the places that use/modify it.
Basically - Ruby is one of the few languages where I feel like global search just doesn't work well, and it also eschews import/require/include statements when used in Rails. It's just a tangled mess, and there's NO way to unwind it without tooling, and even the tooling struggles (RubyMine is a guaranteed way to get my fans running at full speed for large projects, and it's the best I've used).
What's interesting to me about this comment is that among the languages I'm familiar with that you list, the difference between the best discoverability and the worst feels way larger than the difference between the worst one and Ruby. To me, C is barely any better than Ruby; sure, Ruby lets you define methods/types at runtime, but C doesn't even _have_ methods, making finding all the things you can do with a given type way worse in my opinion. Plus, you can still have some wonky generated stuff with macros, although I'll concede that's usually less common than Ruby metaprogramming. Java, C++, and Go are a bit better, since you get a namespace instead of just a random identifier without context, but these namespaces are generally split across multiple files, so in practice I would need to rely on tooling to do this for me, and at least with RubyMine this wasn't in practice _that_ much worse.