Why did the Boeing 747 fail?

Why don't I see airlines using this plane anymore except for Lufthansa and British Airway

Too difficult to fill it with passengers and it was less fuel efficient than subsequent aircraft designs

An aircraft that has been in production for 40 years with almost 1,600 deliveerd is the opposite of a 'failure'.

The reason fewer 747s are in passenger service is due to the US airline industry moving to a hub and spoke system, which uses more but smaller planes.

It is being replaced by newer more efficient and yes more comfortable cabins. 60 years is a very long lifetime of service. It was a very successful design that will still see years of service carrying cargo.

Still works for cargo--especially the really big or heavy ones.
And for experiments--airborne laser, astronomical telescope are a couple I have seen fly.

It didn't "FAIL". In fact, it has been one of the more successful aircraft designs of all times. It's just that the design is more than 50 years old, and airlines are going for newer, more modern airplanes that are more fuel efficient.

It did not fail anymore that the Model T or Volkswagen Beetle failed - they were huge commercial successes that were superseded by later designs.

Part of the reason the 747 was replaced was a change in regulation. When it debuted, twin engine planes were not allowed to operate on oceanic flights. As engine reliability improved, the ETOPS (Extended Twin Operations) limits were extended.to the point where twin engine planes could fly most routes. Since twin engine planes burn less fuel than four engine planes, they were more economical to operate and have almost completely squeezed 4 engine planes out of the marketplace.

It didn't fail; it is simply no longer pertinent.

The original 747-100 carried (typically) 366 passengers over 4620 nm using 48445 US gallon of jet fuel; the -400ER has 416 seats, a range of 7670 nm and 63705 US gallon.
Now compare with the 777-300ER: 365 passengers, 7370 nm range using 47890 US gallon.

The 747-400ER uses 0.019965 gallon of fuel per seat-mile, while the 777 uses 0.0178 gallon per seat-mile, over essentially the same range.
That is 12% less.About 15 gallons less per passenger over 7000 nm. At over $5 per gallon, that is at least $75 less per passenger. When you consider that airlines would go cheap on $10.50 in flight meals, imagine their reaction with not spending an additional $75 in fuel for each passenger.

Larger jet engines are more efficient, so two very big engines will use less fuel for the same performance as 4 smaller ones with about the same overall thrust.
And with 2 engines, there's less maintenance work required than with 4.

It has been in production for 40 years. It's STILL being built and sold. That's far from "fail".