Biggest problem is it doesn’t fit in existing terminals. That’s why Boeing didn’t go for the jump to super-duper jumbo jet. They’ve gone through those growing pains before and saw the market wasn’t good for doing it. A plane you can’t actually use (at least not conveniently, who really wants to ground load a plane that big) doesn’t have a market.
Boeing is betting on smaller, longer range aircraft for point to point air travel. Essentially reworking the hub and spoke airline model. Hub and spoke made sense back when the only long range aircraft were the jumbos.
That’s no longer true.
But what happened was Boeing's unexpected success with the 777-300ER and the strong sales of the 787-8 and 787-9, which has proven that passengers want point-to-point long-range flights, not hub-to-hub long-range flights. Indeed, the 787-9 made it possible for several Chinese airlines to fly from multiple cities in China directly to western Europe and the USA at reasonable cost.