We can literally directly image the accretion disk around a black hole in a galaxy a million light years from here. But an alien spacecraft at 1/4 mile looks like a sun glare on the cockpit window. Strange.
Long reply but the answer to your question might be hiding inside the question itself. The very reason we can photograph the accretion disk around a black hole is precisely because of how black holes affect light. Gravity bends it. That bending of light is what makes the image possible in the first place.
Now apply that same physics to a craft that generates a localized gravitational or electromagnetic field strong enough to neutralize Earth’s gravity and pull off the speeds and angles these things seem to move at. Light approaching that field wouldn’t travel in a straight line to your camera lens. It would bend around or through the field the same way it does near any massive gravitational object. Your camera, and your eyeballs for that matter, would receive photons that originated behind the craft, not from it. You wouldn’t see the craft at all. You’d see whatever is behind it. The field makes the craft functionally invisible not because it’s transparent but because it’s redirecting the exact light that would have revealed it.
There’s a secondary problem too. Fighter jet cameras are optimized for imaging conventional objects that reflect light predictably. A craft wrapped in a dynamic field that’s constantly shifting as it maneuvers would produce an image that looks like a smear, an orb, a heat distortion, a little black spot with a ball around it, or just nothing. Not because the camera needs an upgrade but because the physics of what it’s trying to capture are actively working against it. One thing photography absolutely requires is light moving in a predictable straight line behavior. If you move during a long exposure, your portrait is blurred.
It sounds crazy but none of what I’m describing is technically outside the realm of known physics. To offset Earth’s gravity all you need is a material (or series of materials) capable of generating a repulsive magnetic field equal to 9.8 meters per second squared.
Think of it like the high speed maglev trains which travel up to 600 km/hr not by fighting gravity, but by repelling against a magnetic field beneath them and float. The only difference is the train has a dedicated rail with a known consistent field to push against. A craft doing this in open air would need to manage the inconsistency of Earth’s natural magnetic field in three dimensions, which is a harder engineering problem but not a different physics problem.
We don’t know how to produce those materials yet but we are getting closer. Elements 115, 116, 117, and 118 were all recently added to the periodic table. Nobody actually knows how high that table goes. If it extends significantly beyond where we are now the properties of those unknown elements are genuinely unpredictable from where we currently sit.
That repulsion versus propulsion method of movement may also explain the crashes. Earth’s gravitational field averages 9.8 meters per second squared but it isn’t uniform across the surface. Geological features, ore deposits, and magnetic anomalies create variations. If your craft is calibrated to navigate against a predicted field strength and you fly into an anomaly stronger or weaker than expected, your control system gets bad inputs at the worst possible moment. What was stable flight a second ago suddenly isn’t. That’s not a malfunction. That’s a craft that ran into physics it wasn’t prepared for. A maglev train would have catastrophic problems if the rail beneath it suddenly changed field strength without warning. Same idea, much higher stakes.
The irony is that the same property that makes them impossible to photograph is probably exactly what makes them capable of the performance we keep seeing reported.
…one more thought worth adding. Just like religious theory is bound by what humans have been able to observe and experience, our understanding of physics is exactly the same. We built our models from what we could see, measure, and test from our small corner of the universe over a few hundred years of modern science.
Once you leave those known conditions literally anything is possible.
A civilization that developed independently around a different star with different raw materials and millions of additional years of science behind them may operate from a framework where everything we consider impossible is just Tuesday. Our physics isn’t a universal law handed down from outside. It’s just the best model we’ve been able to build so far from where we’re standing.
Assuming that model captures every constraint that actually exists in nature is the same mistake every generation of scientists has made right up until the moment someone proved them wrong.