Some of the issues are totally language-related. > It’s hard to reason about code when it does something entirely different depending on what code has executed

Some of the issues are totally language-related. > It’s hard to reason about code when it does something entirely different depending on what code has executed in the runtime before it. > What we really need are more explicit guarantees on every line of code that we write [...] than what Ruby can provide Maintenance has a cost on any language, but in some cases you also have to make up for the lack of guarantees the platform gives you. Tooling, as you said, can help, but substantial effort is required to develop and mantain, say, a (production-grade) static type checker. You can't just tell $random_ruby_dev to "help improve tooling" if there is no tooling to begin with.