The perception of taste is remarkably complex, not only on the tongue but in organs throughout the body.
The idea that specific tastes are confined to certain areas of the tongue is a myth that “persists in the collective consciousness despite decades of research debunking it.” Also wrong: the notion that taste is limited to the mouth.
https://onlinelibrary.wiley.com/doi/10.1002/fft2.407
There is utility to being able to detect the presence of the things different tastes are supposed to detect (protein, sugars, acid, salt, toxins) at various points in the digestive tract as well, so your body know when to do things like empty the stomach or release certain digestive enzymes in the gut. Or make you vomit if you eat something toxic.