WRT poor APIs, I'm talking about things like matplotlib or pandas or etc that take a whole slew of arguments and try to guess the caller's intent by inspecting the types of the arguments. The referent isn't "some other scientific computing API" (although I'm sure there are some sane scientific computing APIs), but rather "other APIs in general" since there's nothing inherent to any particular domain that demands this kind of 'magical' API.
WRT 'hardly anyone is CPU bound'--the context is numeric computing; what are people bound by if not CPU? I've seen several projects where web endpoints were timing out while grinding in Pandas, largely because there weren't good options for taking advantage of multiple processors. Based on prototypes I did, I'm confident that other languages could serve those requests in single-digit seconds if not sub-second.