When it comes to airplanes, bigger isn't necessarily better. I guess the novelty value has worn off and giant jets like this have limited appeal. If there was a significant cost saving (there isn't) then of course it would make sense, but due to the limited number of airports that can service these planes and the high cost, I don't see much future in them. The efficiency just isn't there.
The A380 was a bet that the hub and spoke model (where passengers travel to an airline's hub in small planes and onwards from there in larger ones like the A380) would continue to rule the industry.
Instead, what happened was low cost carriers flying passenger directly to the destinations. It appears that passengers prefers that, which is why the B797 and A350 exists.