I think the specific connection to the original post is that there are four separate language features that do related but subtly different things, and the differences and interactions between them are difficult to wrap one's head around. I'd like to think that, if you were designing a language's constant/compile-time evaluation features from the beginning without concern for backwards compatibility, you could come up with something equally powerful but conceptually simpler. (One could argue that this is what Zig has done.)