Regarding maintainability ("hard-to-follow"), I’ve become a big fan of Java’s checked exceptions (and also their causal chaining and adding of "suppressed" exceptions, which would be nice to have for C++ destructors). I effectively see them as a sum type together with the return type, just using different syntax. It’s an important reason why I stick to the language, because no other language has that kind of statically-typed exceptions.
As the article explains, the problems in C++ are more an ABI issue than a programming language issue (except for the by-reference vs. by-value semantics). You could implement exceptions internally by variant-like return values, for example, similar to how error passing is done in Rust, while still having it look like exceptions on the language level. It would be fun for future languages and runtimes to more easily be able to switch the underlying mechanism, or possibly to be able to use different implementation mechanisms for different parts of a program as needed.
As the article explains, the problems in C++ are more an ABI issue than a programming language issue (except for the by-reference vs. by-value semantics). You could implement exceptions internally by variant-like return values, for example, similar to how error passing is done in Rust, while still having it look like exceptions on the language level. It would be fun for future languages and runtimes to more easily be able to switch the underlying mechanism, or possibly to be able to use different implementation mechanisms for different parts of a program as needed.