I am not a fan of this show. It's wierd because I admit it's cleverly written with great characters and what not, but it just doesn't hold my attention.
I'm too spoiled from it's always sunny and trailer park boys :/
I think they just kept Adam Reed's signature style from Sealab 2021, which probably could only get made because it was animated on the cheap using cels from a 70s cartoon called Sealab 2020. I'm guessing they went with it as an ironic homage to the fans they were hoping would migrate to Archer from earlier work who were already accustomed to its makeshift charm. It's cheap, but, like in South Park, occasionally the rigid paper cut-out look works comedically for anti-climatic and style contrast effects, e.g. epic crashes and gratuitous blood scenes.