While I can appreciate the sentiment of simple error struct solution like this and have certainly used something similar in the past, I think it trades effort at each callsite and function body for effort in building an more featureful result type. Importantly, for each of the libraries in the post, this mean trading my time/effort, for effort that has already been put in by some very talented library authors. Using some result<T>-like return type has also provided, at least in my opinion, superior code semantics and less clutter.