The theremin is cool because it’s weird though. And being able to play it is impressive in part because it is difficult.

But most of all what I like about the theremin is that it is an electronic instrument all of its own unique kind and not an emulation of the instruments that existed before electricity was usable by humans.

Saying that a cello is “strictly better” than a theremin kinda feels to me like saying that ice skating is “strictly better” than rollerblading. It’s just different activities that different people enjoy.