The new “Downton Abbey” film proclaims that it’s “A New Era,” but in actuality, it’s a real throwback. It’s not just that “Downton Abbey: A New Era” is a shiny replication of a world that’s nearly a century old, but it’s also a reminder of the world that we lived in when we loved “Downton Abbey,” those heady days of the 2010s when we gulped down seasons of the wildly popular, award-winning historical TV drama created by Julian Fellowes. Watching it feels like double escapism: to early 20th-century England, as well as to a pre-pandemic time. The series “Downton Abbey” did engage with political …