Machines? So all their talk about not being particularly good with machines was just a smokescreen?
Basing that solely on the line where the Talosians insist that humans could be taught. Humans can't be taught to grow giant gross 50s sci-fi brains. Well, maybe they could via genetic tampering, but I think machines make as much or more sense.*
I always interpreted the Talosians as having built a large illusion-casting industrial complex that was largely automated, but over the decades, centuries, and so forth they became too endumbened and lazified by their Total Sense Internet to ever build anything else more complicated than an elevator or pane of glass.
It's actually little surprising that The Cage was never broadcast back in the day, given its message, and it's even more surprising that it remains one of the more relevant Trek episodes even ~fifty years later.
*On the other hand, a fair amount of early Trek is under the goofy impression that humans have latent telepathic abilities that need only a crazy radiation bolt or the love of a good plasma-cloud man to be jumpstarted. This was pretty much retconned out, of course.