"... I look at it on my MacBook Pro it’s very ugly...????"
What are you exact settings? Reset your camera...fully. Set it to P mode. Set ISO 200, auto WB. Go outside on a nice sunny day and take some random shots. Look at the photos. Are they OK or do they show noise? If they are OK there is nothing wrong with your camera. That means you either have difficult shooting conditions where you experience the noise or you set the camera incorrectly for the subject.
Do as Ernie says.
"The RP should be useful in dark area but when I look at it on my MacBook Pro it’s very ugly...????"
Dark area is a subjective term. What are the shooting conditions? What is the ISO that the camera/or you have set.
The RP is not ISO invariant, so it is important to choose the approriate ISO for the shooting conditions. Better to choose ISO 6400, for example, then to select ISO 1600 and boost exposure in post by two stops.
What you must understand is ISO in a digital camera is an electronic term and not a photography spec. OK, they use a similar measuring system so we can use it in photography but it actually is using more electricity, amplification, to do so. The base ISO of a sensor is its common state. When you want it to be more sensitive, a higher ISO if you will, you need to amplify the sensors output. This causes "noise". Its the very same thing you might notice in your stereo amplifier. As you turn up more and more volume you get some distortion in the sound.
The lowest ISO number may not be the cameras base ISO number. ISO 100 could be but some ISO 200 might be. Some tricks are done to "slow" the sensor sensitivity which may also introduce noise.