The drive between Anchorage and Denali takes about four and a half hours. The train takes longer, and that's the point.
The Denali Star runs along the Susitna River valley, past the Talkeetna Mountains, with the chance of a first glimpse of Denali itself on a clear day (no guarantees. She's shy, and famous for it). Full-length glass-domed viewing cars mean you're not craning your neck out a window, and a dining car serves meals made with Alaska-sourced ingredients along the way.
There's no driving, no parking, no watching the road instead of the scenery. Just wildlife spotting from a comfortable seat and roughly eight hours of Alaska passing by the window, exactly as it should.