I never interpreted the Cow Tools strip as saying "cows are too dumb to use tools", but more along the lines of "if cows could create tools could we even fathom their use?" - kinda like the Borges story, Celestial Emporium of Benevolent Knowledge[0]. On the other hand, I read The Far Side when I was small and didn't really have the scientific chops to get a lot of the humor, so maybe I cemented an incorrect interpretation.

[0] https://en.wikipedia.org/wiki/Celestial_Emporium_of_Benevole...