Is there something about CCR that I am missing?

You have to take art in the context of its time. They were a great band in their day because their music was real, downhome, folksy, and accessible. CCR, The Band, Flying Burritos, & Dylan's John Wesley Harding/Nashville Skyline persona were the pioneers of the first Rock revivalist movement (precursors of Punk and Grunge) that lead us out of the psychedelic wilderness and back to our roots. That's why they are well regarded.