Somewhat downplaying it. Charles is easily the most popular tool for reverse engineering client-server communications in mobile apps.
Certificate pinning frustrates Charles by hampering MITM attempts. It can be difficult to extract/replace pinned certificates from the latest versions of Android/iOS apps. Often you can extract them from older versions using specialized tools, if old-enough versions exist and those certificates are still valid for API endpoints of interest.
It's like saying IDA Pro is just an interesting piece of software for looking at binaries, but the grandparent comment is surely from someone who doesn't look at these utilities, so I guess that's why I didn't press it.
