You can talk about things you worked on after they ship and are publicly known.
It's important to remember people who really love their job and do well don't tend to leave so you almost always get stories from people who don't fit that description (though not always - sometimes people leave a workplace for personal reasons).
People leave all the time, for all sorts of reasons, e.g. to get side-promoted, to work on something different, to get more money.
I've seen the opposite of your thesis -- that people who have opportunities and actively work on their careers tend to change jobs often so whoever does not must be stagnating.
It's important to remember people who really love their job and do well don't tend to leave so you almost always get stories from people who don't fit that description (though not always - sometimes people leave a workplace for personal reasons).