You know, Boeing clearly have the expertise and experience to build the best passenger jet in this sector of the market, so why have they persisted all this time with ever more modified 737s?
Plainly, the original design was good, and it could stand some enlargement, but with any design there comes a point where the possibilities for modification and improvement are exhausted. Looking at some of the larger NGs or the P-8 shows how far they came- and safely.
But adding the LEAP engines was clearly a step too far. The 737 really needed a redesign into what would effectively be a new aircraft to accommodate the new engines, so why wasn't it done?
If this jet is to return to the skies, it should get what it needs- new undercarriage, probably the wing repositioned on the fuselage, the engines where they should be, and many other changes. It will be too much of a change for the existing jets, but the MAXes could probably be modified into useful 737 variants using normal engines.
Boeing need to get a grip. There's more to a company than just money and profit- there's also product.
They should do what they know, better than anyone, needs done.
Accept the sunk losses, repurpose the MAXs' into something else.
Start on their A320, GTF engined competitor from scratch, restore their reputation, and make a damn good job of it.
Go on to sell thousands of them, and make a fortune.
edit. The MAX has LEAP engines, not GTF. Although both are much bigger and powerful than previously fitted power plants.