In the context of C++ it means that you don't have to make changes to your code when a new language version comes out. Because old broken features are preserved

In the context of C++ it means that you don't have to make changes to your code when a new language version comes out. Because old broken features are preserved for eternity even if severely dysfunctional. Most of the hard work of learning C++ is learning all the "gotchas" that will sneak in and cause undefined behaviour or worse. That's why people have a love/hate relationship with it. The language is full of BS but the path of least resistance is to learn the ins and outs of the BS rather than to do a full rewrite of your huge codebase in a sane language. Learning the ins and outs of C++ is a one time hit, after that you can use it quite happily. So new projects get started in C++ and the cycle repeats.