They are basically right though.
The counterexample of some Unix utilities means nothing. You're not getting a CS degree in order to develop the next version of cat, are you?
We have some things with a long history and they are easy to identify. It is just hindsight being 20/20.
For every one of those things, there are countless that can't be seen or felt. They aren't here; they got washed away.
Who uses the Michigan Terminal System?
Or a web framework from ten years ago?
The aunt and the cousin are thinking that 'computer technology' exists at the level of abstraction of the sandcastles in the metaphor. To some extent it does, but the vastly greater part of it is at the level of abstraction of the knowledge and theory of building sand castles, as gained over the course of many iterations.
One of the most common themes one hears, when reading what people write about computer science, is how few new ideas in computer science are actually involved in nearly anything anyone does on a computer (or teaches at the undergraduate level).
Well, I still write ASP.NET Web Forms on a regular basis. Ten years is not that old, or is it? Though it is harder and harder to find developers for it, the young people simply don't start with Web Forms.
They are only right in the same way that a physics major is obsoleted by advances in physics: lhc, discovery of dark matter & energy, increasing expansion of the universe, etc.
A CS major isn't about learning the latest Angular framework derivative. A CS major is about learning fundamental aspects of computer science.
Indeed, the observation that some Unix utilities have their roots in the seventies misses the point in this regard. I'd say this is a testament to the success of the unix approach or whatever you want to call it. It's not really about computer science.