See my other comment for more detials but it kind of destroys the type safety of the language. In Java for example, it lets you modify private/protected fields and call private/protected methods.

It’s also slower than accessing a field normally since you need to do a string lookup (but slightly faster than a hashmap/dictionary) so if you use it over a large enough list it’ll cause slowdowns.

Most use cases for it in Java/C# revolve around testing, serialization, and dynamic filtering/sorting. And most of those cases can be handled more safely using macros/attributes (EDIT: and templates as well, though those are also pretty painful to deal with) because that gets handled at compile-time in C/C++.