I'd call tools like ASAN and friends debug tooling. I'm not sure if zig has tooling that doesn't have an analogue in the c++ world, but having them built in to the compiler by default is a notable feature.
Right, defaults matter. The fact sanitizers exist is much less of a game changer than the default behaviour being sanitized.
Because C++ defaults are notoriously all wrong, in programming language design you could usually do worse than consider, "Is there an alternative to what C++ does here by default?" and if there is one, choose that alternative as your default because it's more likely to be correct.
Sometimes C++ helps you out, it might have a keyword "do_it_right" and you can just default to that, if you feel people might want the C++ default behaviour, feel free to reserve "do_it_wrong" in case people wanted that, but in many cases they will never ask you to implement the C++ behaviour because it's just wrong. Examples: "const" in C++ doesn't mean "constant" it means "immutable", so, make immutable your default and offer "mutable" as the option. "explicit" in C++ makes constructors need an explicit cast to be used for conversion, once again of course you want that by default but feel free to reserve "implicit" in case some people are sure they need the C++ behaviour.
C++ frameworks pre-standard used to have better defaults, unfortunately there a majority of people voting that would rather have the wrong defaults, and so here we are, and given how ISO works it won't change.
Those that care know where the knobs are to re-enable those proper defaults, given that for some domains, C++ is going to stay around for a while, regardless of the alternatives.
