The reason MH370 is so difficult to find is because the pilot turned off all tracking except one Inmarsat beacon that he was unaware of.

The Inmarsat beacon only provides timing pings, which means it can only be used to provide an arc of distance away from the satellite receiver. Not an exact location.

What complicates this further is that the distance pattern changed for the last ping. It was not evenly spaced apart like the previous pings, it was much closer to the previous ping, meaning that the aircraft had changed course between pings.

To make things much worse, multiple simulations completely ignored this and gave faulty information based on fuel burn simulations, while ignoring the ping data. They literally go right past the ping and keep going. Making them basically useless. In fact, they cause more harm than good.

The search teams assumed that the change in ping meant the aircraft had turned and flown south. So they concentrated their efforts on the southern portion of the arc.

But this turned out to be incorrect. Because the last ping change doesn’t necessarily mean a turn. It just means velocity away from the satellite receiver changed. It can have multiple meanings besides a turn south.

There is a system called WSPRnet that has shown the ability to track aircraft passively using radio transmissions as a form of radar. This system was used to attempt to recreate the flight path, and appears to show the aircraft going into a holding pattern at the last ping line. All of the WSPRnet data matches the ping data, and it has been proven by tracking thousands of other aircraft during tests. So there is an extremely high chance that it is correct and the aircraft did not turn. It probably entered a holding pattern North of the search areas.

To make this much more complicated, the current spread debris over a huge area. So it might not even be possible to find the main wreckage. It might be in bits all over the ocean floor.

So the best that can be hoped for is that some large chunks or engine components may be found one day. And if the aircraft floated at all after crash, they are unlikely to be directly at the point of impact.

This obviously makes finding the wreck an absolutely daunting task.