Here's the thing.
No matter what you do, you're going to have the six fundamental machines floating around there in some form. 'Mechanisms' is a deliberately vague term that can imply a lot of things. One of the most devilish things about a lot of traps is how simple they are in their execution. Animal traps may well have been among ancient man's first automatons.
Things like weapon traps seem to imply a higher level of engineering prowess than kobolds might have, but what does, say, the giant spiked ball trap bring to mind? A swinging spiked ball bashing the shit out of some poor guy - and a simple tethered weapon swinging on a rope. That sword trap could be a bent pine bough ready to swing with a sword tied firmly to its end. Serrated discs and pressure plates are pushing it, but I think we take for granted a lot of what primitive people could do. (The biggest problem with ancient engineering is that it wasn't yet a science. People knew things happened, but had no idea how or why, and thus couldn't refine their inventions as precisely.)
Assuming kobolds have human-level intelligence or at least something close to it, there's no compelling reason to handicap them other than their civilization simply not being as technologically mature as the others for some reason. Recall that most Native Americans were still practically in the stone age when colonists with steel, ships, and gunpowder arrived in North America.