> So there's obviously no such thing as "just an error" from that alone

The point is that all values are potentially errors. An age value, for example, can be an error if your business case requires restricting access to someone under the age of 18. There is nothing special about a certain value just because it has a type named "error", though.

Let's face it: At the root of this discussion is the simple fact that "if" statements are just not very good. They're not good for handling errors, but they're also not good for handling anything else either. It is just more obvious in the case of what we call errors because of frequency.

Something better is sorely lacking, but seeking better only for types named "error" misses the forest for the trees.