At best, you get an impressionistic version of the original scene. Think of it like restoring a shredded document by looking at the spaces between shreds—you see the outline, never the text.
The phrase represents the clash between bandwidth constraints and the human demand for perfect vision. No algorithm can recover data that was never recorded—if a face is a 4x4 block of grey, it’s gone forever. However, modern reduction techniques can turn a "blocky mess" into a "smooth, watchable experience" by intelligently guessing the missing texture. ssis698 4k reducing mosaic