Hard disagree, esp re "only useful for a software developer familiar with the codebase". Too many "user-friendly" apps create "helpful" error messages that hide essential information.

"Cannot open data file: Not found" and that's it - no more context (such as a filename). Even for a user with no coding experience, this is absolutely useless, you cannot find good explanation for it on the Google. A backtrace might look ugly, but at least would have a much higher chance to point to a useful forum post. And now with AI advances, AI can analyze backtraces and sometimes give an explanation (not very often, but there is no alternatives...)

So by all means, add a nice, human-readable error message for a few common cases that user likely to encounter, such as "internet down" or "wrong type of input file"... but leave backtraces on for all other unexpected cases, like "server returned nonsense", "out of disk space", etc....

A backtrace won't give you the values of variables needed to identify that.

I did specify "succinctly as possible with all the information necessary for a human to be able to solve the issue". An error that doesn't have "all the information necessary" is a bad error. It can be worse than a backtrace. That doesn't mean a backtrace is good.