There was an article from about a year ago, before the crashes, where the author, almost predicting the future, said that what Boeing needs now is the 757, which had been cancelled years ago. The reason was that airlines were wanting more capacity on relatively short haul flights and travelers were sick of regional plane (smaller ones), and the 757 virtually matched their needs. The 757 sits higher, and has its engines where they belong, under the wing, rather than the goofy Max, which practically has them in front of the nose, due to sitting so low.
But I suspect that the plans and tooling have been ‘recycled’ so as to save storage costs. Not the first time aerospace companies have done the same, just plain stupid. You rent a warehouse outside of Seattle for $3,000 or so a month, throw in all the key tooling, have a relatively small climate-controlled area for the design and certification documentation (carefully indexed), hire a contract guard or two, and put in an alarm system (they can get 24 hour monitoring for less than $30 per month). Utilities are next to nothing in Seattle due to the climate, and so you run the operation for maybe $10k per month, and if you want to resurrect the 757, even 20 years later, it’s all there, and you paid $2.4M for all those years, whereas starting again from scratch would cost well into the billions.
Go figure.
The 37’s have gone through a number of improvements over the course of their operational history, none of which required a name change or a new type rating. The originals had low bypass engines, stubby wings and were relatively underpowered. I swear the wing engineering was a touch off, as the aircraft cruised at about a 3 or 4 degree pitch up. Cabin crew always felt like they were working on a slope. That all changed with the NG models with a new wing, entirely updated avionics and bigger hi bypass engines. All of this accomplished without a real name (737 NG) change or requirement for a new type rating for pilots. The MAX is the 3rd iteration of the venerated 73s that have possessed a top safety rating for 20+ years.
...Just to give a bit more historical perspective.
Uh, you might want to Google images of the 757 to see where the engines are positioned. Google A321, 737NG and 737MAX while you're at it for comparison. They're all in the same spot, and that spot is not under the wing.