They're one of the only insects that show hunting behavior, as in pattern recognition and path planning [1], with brains so large that their esophagus has to go through it, to fit, with one of the largest brain to body rations of any animal. And, they dance [2]!
Edit: Here's an evolutionary tree: https://en.wikipedia.org/wiki/Arthropod#Evolutionary_history.... Insects are a group under "Hexapods", and are more closely related to crabs, lobsters, shrimp, centipedes, and millipedes (none of which are insects) than they are to spiders, which are under "Chelicerates".
Yes, but does your esophagus get pulled out every time you shed? I think not!
And, you have simple fixed zoom balls for eyes, where they have muscles that point little telescopes [3], that pivot at the eye hole, each with two lenses, allowing control of focus and magnification.
They're not insects at all. They're spiders.
Edit: Here's an evolutionary tree: https://en.wikipedia.org/wiki/Arthropod#Evolutionary_history.... Insects are a group under "Hexapods", and are more closely related to crabs, lobsters, shrimp, centipedes, and millipedes (none of which are insects) than they are to spiders, which are under "Chelicerates".