The reason we still have long-distance train service is that it (1) serves rural communities that have few or no other public transportation alternatives, and (2) it serves people who can't fly or drive due to medical reasons. In addition, there are travelers who just prefer to ride on the train. The vast majority of long-distance train riders are not riding coast-to-coast or even on overnight trips. They are well served by long-distance coach, which has roomy seats and is reasonably priced.
The premium services have a value to Amtrak in that they generate considerable additional revenue for the train, thus improving it's "financial performance" (a term I prefer to use over "profitability." Because these are cash cows for Amtrak, the company is, of course, going to want to charge as much as they can for these services. If the sleepers are being filled at high prices that many here think are not a good value, that means that there are other people who believe that they are a good value. The problem with going overboard with amenities, such as enhanced food service, is that the cost of the amenities might significant reduce the net revenue coming from the premium service, and thus reduce the value of providing premium service as a way to cross subsidize the trains' financial performance. It's hard to argue about the cost of such and such a level of service, as Amtrak's accounting practices appear to be opaque, indeed. However, many of us who patronize the dining cars do seem to notice that Amtrak management does not appear to be running the dining cars in a way that could maximize revenue from them, so it's indeed possible that with changes in policy and procedures, the dining service could provide more revenue at little extra cost, thus improving the value proposition of the premium sleeper service, even for the demanding tastes of many here on AU.
As far as travel times, the trains should be operated in a way that the travel times are roughly the same as normal travel by car, which means a point-to-point average speed of about 50 mph. This is, in fact, the usual end-to-end average for most of the long distance trains. This is, in fact, faster than driving for long trips, because the trains don't stop for bathroom breaks, meal breaks, or to spend the night. The problem seems to be that the long-distance trains are commonly late, which means that Amtrak's first priority should be getting them to operate on schedule. Aside from stuff under Amtrak's control, like making sure the equipment is well maintained and doesn't break down, this means doing stuff like pressing the courts to enforce the dispatching priority for passenger trains that's encoded in the law and getting funding for construction projects that could ease bottlenecks in critical locations.
While I wouldn't expect a coast-to-coast train trip to be in any way comparable to a coast to coast airplane trip, I have used long distance service for business travel with train rides of up to 20 hours. The most important thing for using the train under such circumstances is that the train arrive on schedule, or early. And a coast-to-coast sleeper may well be price competitive with driving. According to AAA, fixed and operating costs for a car driven 15,000 miles per year is 62¢ per mile. That means a 3,000 mile road trip will cost $1,860. In addition to that, there is the cost of lodging and food for the 4 to 5 overnight stops you'll need to make. So maybe that $2,000 Amtrak bedroom for the three nights on the train between NY and LA isn't as expensive as you think.