I'm not arguing that stack frames are as good as manually written error traces can be - they're clearly not. I am simply amazed that people include "generate error traces" as a form of "handling" an error.

The argument for explicit error values is often something like "it encourages people to actually handle their errors, rather than ignoring them". And on the face of it, this has some merit: we've all seen code that assumes an HTTP request can't fail, and now a small timeout crashes the entire backup procedure or whatever.

But if "handle the error" simply means "decorate it with a trace and return it", then exceptions already do this, then you're really admitting that there is no fundamental difference from a exception, because this is exactly what exceptions do, all on their own. Sure, they produce less useful traces, but that's usually a tiny difference. After all, the argument wasn't "you'll get better stack traces than exceptions give you", it was "people will be more careful to handle errors".

This is also relevant, because if the goal is to get better error traces, that can also be done with exceptions, with just some small improvements to syntax and semantics (e.g. add syntax for decorating a call site with user supplied context that will get included in any exception bubbled from it; add support in an exception to only print non-library stack frames, add support in the language to declare certain variables as "important" and have them auto-included in stack traces - many ideas).