I don't think error handling is a solved problem in language design
There are certain things about programming language design that are more or less solved problems, where we generally know what the good and bad approaches are. For example, over time we've wound up agreeing on various common control structures like for and while loops, if statements, and multi-option switch/case/etc statements. The syntax may vary (sometimes very much, as for example in Lisp), but the approach is more or less the same because we've come up with good approaches.
I don't believe this is the case with handling errors. One way to see this is to look at the wide variety of approaches and patterns that languages today take to error handling. There is at least 'errors as exceptions' (for example, Python), 'errors as values' (Go and C), and 'errors instead of results and you have to check' combined with 'if errors happen, panic' (both Rust). Even in Rust there are multiple idioms for dealing with errors; some Rust code will explicitly check its Result types, while other Rust code sprinkles '?' around and accepts that if the program sails off the happy path, it simply dies.
Update: I got Rust's error handling wrong, as pointed out in the comments on this entry. What I was thinking of is Rust's .unwrap() and .expect(), not '?'.
If you were creating a new programming language from scratch, there's no clear agreed answer to what error handling approach you should pick, not the way we have more or less agreed on how for, while, and so on should work. You'd be left to evaluate trade offs in language design and language ergonomics and to make (and justify) your choices, and there probably would always be people who think you should have chosen differently. The same is true of changing or evolving existing languages, where there's no generally agreed on 'good error handling' to move toward.
(The obvious corollary of this is that there's no generally agreed on keywords or other syntax for error handling, the way 'for' and 'while' are widely accepted as keywords as well as concepts. The closest we've come is that some forms of error handling have generally accepted keywords, such as try/catch for exception handling.)
I like to think that this will change at some point in the future. Surely there actually is a good pattern for error handling out there and at some point we will find it (if it hasn't already been found) and then converge on it, as we've converged on programming language things before. But I feel it's clear that we're not there yet today.
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