Actually Amtrak does do a fair bit of marketing, but it shows up mainly in major markets like NY and other large cities. And not all the marketing that I see and/or hear in the NY market is about Acela, although probably 70% of it is about Acela. There are ads from time to time touting long distance trains.

As for why they don't use your suggestion, that being "a land cruise", it's not done because too many critics already consider Amtrak to be a land cruise and therefore unworthy of Federal support. They argue that the Fed doesn't support sea cruises, so why should tax payers pay for land cruises for the rich.

Of course it isn't just the rich who ride Amtrak trains, but they don't want to hear about that part, they just see sleepers and figure that they are subsidizing someone's luxury vacation. Those assumptions are of course incorrect, but that doesn't stop them from claiming that it is true. The first assumption being that an Amtrak sleeping car is the lap of luxury. The second that only the rich and/or railfans ride the long distance trains. The final being that they are subsidizing the sleeping cars.

The reality is that the sleeping cars do pay for themselves. The Fed is still subsidizing the basic railfare that all travelers on Amtrak pay, although the subsidy is less for a passenger in a sleeper than it is for a passenger in coach. But the Fed is not subsidizing sleepers.