I talked to a buddy a few days ago who is currently working the 777X (specifically the -8F). I asked him why the program was taking so long. For a while it was 'all hands-on-deck' to fix the MAX, later on the same thing to get 787 deliveries going again. So resources were directed away from the 777X - but now that stuff is pretty much handled, what were the holdups?
He said the FAA was establishing all sorts of new requirements for cert - but hadn't figured out how to implement them yet. So it was being pretty much made up as they went...
Somehow I don't think this is going to be an improvement. 
