It's a very half baked paywall, The Atlantic limits you to one or two articles a month before they want you to subscribe or use some other trivial workaround such as incognito
When I encounter a site that does this, I block it from setting cookies. In Chrome, it's 4 clicks: padlock icon -> "Cookies" -> "Block" -> "Done". I've only seen one site that tests for this; for the rest, it permanently disables the paywall.