Boeing can't even keep its newest plane in the skies, and may have killed off the 737 line for good. Think another revision after the MAX is ever going to be approved?
Their product and their brand are worse than bad, but they make a lot of money.
Yes, I agree the 50 year old design seems to have reached its end of life.
The KC46 is being fielded by the US and a few nations that the US traditionally use the same arms.
The A330 is fielded by the UK, a couple commonwealth nations and KSA
Total number built is in the 30s for both.
* https://www.thedrive.com/the-war-zone/29933/air-force-says-i...
* https://www.aerotime.aero/clement.charpentreau/24184-no-fix-...
Everything would have been fine except there was so much pressure to make every change as modest as possible that it didn't quite all work. They needed to either make significant changes to the landing gear or significant changes to the flight control computer and they chose neither.
The 787 is the newest airframe and it's fine. The 737 is the Windows XP of the sky and there's only so much you can fix with service packs.
How about the KC-46 and 777X?