Layovers and plane changes in Atlanta used to be so common there were numerous jokes about having to stop in Atlanta no matter where you were going - like saying to fly from Chicago to NY you would have to change planes in Atlanta.
The fact is, regardless if you want to separate trains by labels like "Long Distance" or "Regional" or "Corridor" - LD trains fill all those slots.
Those going from NYP to MIA are on a LD ride, those who rode from JAX to MIA were taking a regional ride and someone riding from NYP to PHL could be viewed as a corridor train - yet they could all be riding the same Silver train ... so, are the Silvers LD, Regional or corridor?
That is why it does not really work to compare trains to planes. Seldom does the same plane fill all of these categories like many trains do.
It isn't always cut-and-dry like that. There are a number of trains that only dis/embark passengers depending on the location and direction in order to better serve the community. The
City of New Orleans for example, picks up passengers at Homewood, IL, going south and only discharges going north, the idea being to prevent siphoning passengers from the corridor trains or Metra (I think some of the Chicago-area ones are actually non-compete agreements with Metra, especially along the BNSF route). Then there are others, mostly on the NEC, that stop at most, if not all, stations and act like all three services, something I personally disagree with in high-traffic areas. There are plenty of
Northeast Regional services available, why are we stopping an LD service at a smaller station to act like a corridor train? Ending that practice would shave off running time, but it has to be done tactically; there are some locations (like Homewood) who are better served by it because there is no easy way to get back there from Chicago Union Station; you'd have to walk to Millennium Street from CUS to get to the Metra Electric District then head back south or wait for the
Illini/Saluki. But there are others that have so much service it doesn't make sense to stop them there.
You've just described the "hub and spoke" system still widely used by airlines. Simply substitute Delta's Atlanta with the hub city of your favorite airline. We're long-time AA flyers and to save money we've often flown out of Buffalo, NY. Until AA merged with US Air, getting from Buffalo to New York, Boston, etc., involved flying through Chicago every time. Great for frequent flyer miles, but not very time-friendly.
A hub-and-spoke system for Amtrak may not be a bad idea. After all, that is essentially what Chicago is at this point: a massive Amtrak corridor hub. You can connect to other corridor trains (think American Eagle, Delta Connection, and United Express) or to the long distance services (mainline American, Delta, and United). Doing the same for Amtrak could create better connectivity and increase ridership, provided the service has
value for money, is sufficiently quick, and
has VIABLE connectivity.