I would amend that slightly: it *either* has to be roughly as fast as driving, *or* it has to offer me the ability to do something I can't while driving or flying --- for instance, I can sit and read, or work offline on a laptop, much more easily on a train than I can while driving (or while a passenger in someone else's car, or while flying.) In my part of the world, with 80mph speed limits on all the interstates and very few traffic jams, the train never wins on speed alone.
There is a market for slow-but-comfortable. There's a market for moving offices, fully equipped with phone service and fast internet.
There's a market for "isn't it nice to get directly from downtown to downtown without having to be at the wheel in a traffic jam."
None of these markets is "everybody." But they are all legitimate markets. Slower than but more comfortable than a plane is a big market over distances of a few hundred miles. Slower than driving but less stress than fighting traffic and looking for parking describes a lot of suburban service. (And in a few cases - in the NEC, and for instance a subway under a gridlocked downtown - the train is actually faster.)
Now which of those markets should Amtrak stress?
There was a time when the social and relaxed atmosphere was a big selling point. It seems to be less so now (and the lack of wifi and cell service on western trains is turning into a sizable negative.)
Maybe selling electronically capable roomettes to businessmen for day trips is a real new market to consider. Maybe Japanese style sleepers for 10-hour trips is a real new market.
Most of that marketing relates to the onboard amenities. ALL of those markets require the train to be frequent and on time.
