It's the opposite of cellphone camera. It has low megapixels and a large sensor size. This will allow a lot of light onto the sensor and it won't suffer from the noisiness that high megapixels on a smaller sensor suffer from.
The point is that, on the spectrum of all imaging devices you might put on a satellite, both Juno and a cell phone camera are in the same rough neighborhood. They are dwarfed by telephoto lens, or 200 megapixel sensors. Remember especially that the topic we are discussing is the resolution (km/pixel) at a particular distance (see above), and for this the lens are much more important than the particular CCD chosen.
So now it's the lens that you don't like, not the sensor? The imaging camera has a wide angle (11.7mm) because it's going to be so close to the surface that a wide angle is optimal. That's actually a lot wider than cell phones (iPhone 6s is 31mm equivalent). There are also other instruments on board that look through the gas with telescopic reach.
