True, but Shazam is a testament to what's achievable even without audio source separation. Even going back about 10 years when I first tried it, I was kind of stupefied that it managed to work in a noisy department store.
There used to be an an app called Midomi (I think?) that could identify songs by humming or you singing, which was cool, but then I vaguely remember it rebranding itself and being less useful. Does anyone else know of a song-recognition app that is more like BirdNet and less like Shazam?