First off, you don't need to title your comments. That said, just because a codebase is old doesn't mean it has a lot of tech debt; that's down to maintenance,

First off, you don't need to title your comments. That said, just because a codebase is old doesn't mean it has a lot of tech debt; that's down to maintenance, discipline, and setting priorities. There was a blogger which kept tabs on what Apple's iOS (apps?) were being written in, showing a steady migration towards Swift, which tells me they're not just letting code sit and rot.