The CPI is raw data, yes. IIRC, the there are several different CPI's, though they may not call them that anymore, just as there are several unemployment rates. What those numbers cover and how they are derived is all spelled out - the government is quite specific. In any event, the data is all there to scrutinize however you wish to use it.
People who don't trust government data either don't understand the data, don't understand the method of gathering the data, or need to visit the Conspiracy section.