Scientist recently got a good picture of one
The "photo" you're referring to was constructed by a super computer massaging enormous amounts of data to fit a model and constructing an image from weighted averages of thousands of data images across the spectrum from an enormously complex array of detectors in an unfathomably noisy environment [1].
It was presented by the media as a "photo", but it seems to me like it's more similar to the "image" we get from reconstruction of wifi signals in a room to determine interior object's shape.
Or maybe a better example would be the "photos" of atoms, which are not photos at all but a reconstruction of miniscule electromagnetic resistance readings from a STM whisker driven by a piezoelectric crystal.
I think we're supposed to get the ability to have better "photos" with the activation of LISA in 2037 [2] but until then, claiming that we have photos of black holes seems a bit misleading (not by you, I mean the science reporting).
[1] https://eventhorizontelescope.org/blog/astronomers-reveal-fi...
[2] https://en.m.wikipedia.org/wiki/Laser_Interferometer_Space_A...
Because science is about "buying" it?
When?
Are you suggesting that emitting or reflecting visible radiation is required before we can prove something exists in objective reality? Your own point about Wifi signals proves you wrong - we can detect wifi in other wavelengths and thus learn a great deal about it. Just like we can with black holes.
There is no distinction between "images" and "photos" - they're both electromagnetic radiation converted to a visual medium. There's nothing unique about radiation in the 380 to 700 nanometers wavelength range that makes it somehow more scientifically valid for remote sensing.
It's a far cry from just shifting the spectrum a bit to the visible range.
Yes, their methodogy used lots of signal manipulation to produce the photo. Just like an RGB digital camera does. Just like analog film. Just like our rods, cones and visual cortex. Which one is the "correct" way to process the signal?
What you're claiming is that "photos" have privileged scientific status over other types of sensors/processing hardware. Someone else might claim that only biological sensors have privileged status. But neither claim is scientific since it cannot be verified.
In lieu of a testable hypothesis, we have to conclude that all frequencies of electromagnetic radiation and all mathematically-valid signal processing techniques are fair game for empirical observation.