I remember a scene from Titanic that at first showed the giant ship then panned out to the HUGE ocean surrounding it until titanic was just a tiny white dot in a massive sea of black...add 3 miles deep to that.
the oceans are HUGE.
They don’t ever have a chance of finding the plane unless some credible coordinates are established.
I am very aware of the vastness of the oceans.
But watch some air disaster shows. You’ll see something always turns up. Aircraft are built to save weight, and most stuff floats. 4 years and nothing (well, I think they had SOME couple things), even with educated guesses for tracking, is unbelievable.
Even if it went over a land mass, surely something would’ve turned up by now. Difficult, but not impossible if you’re looking.