If you think it is "trivial" to make a bland substance taste good without substantially changing the nutritional makeup of that substance, there are a lot of diet food companies who would like to have a chat with you and make you fabulously rich. Jamba Juice would like to know the secret, too.
Most things that innately taste good -- stuff that you could drop in a blender and drink and it'd still be agreeable -- are fatty, salty, starchy, sugary, or some mix of all these. Healthy and good-tasting food requires pleasant textures and careful composition that allows a small amount of fat, salt, starch, etc. to enhance the flavor of the whole meal.
I guess I should have said it would be trivial to make it tastier for my own non-demanding taste buds. I could just add a few drops of stevia and I'd be good to go, but I see how it could be a challenge to make something that pleases most people.
"Fatty" is not a synonym for unhealthy by the way. A lot of people consider high fat/low carb diets to be healthier than the reverse.
Don't get fries. Don't get a drink with sugar added. Definitely don't get a milkshake or cookies.
The burger itself is fine. You wouldn't go to Subway for a nice sandwich and drink a liter of Coke afterwards and a bag of chips and complain about how unhealthy it is.
Here you can get some nice fresh crispy raw carrots instead of fries.
I choose -- false dichotomy. Plenty of healthy and not tasteless quick meal replacements that already exist.